Moon Bible : Moon Rocks and a whole bunch of Science.

 

 

The Moon is Earth's only natural satellite, an amazing object of fascination for mankind. It's our closest celestial neighbor and yet it has been a mystery for centuries. The Moon is our loyal cosmic companion and we've been Moon inspired for quite long time. It's a prominent view in our night sky reflecting sunshine as moonshine on us especially in the darkness of night. It has been always an inspiration, a source of fascination and curiosity. It has inspired a rich cultural and symbolic tradition throughout our history; the inspiration that made better and better version of us. For example poets and philosophers inspired to write fresh poetry, thoughts, philosophy, perspectives. Also for astronomers to reach stars, galaxies and edge of the universe while for scientists, engineers and technocratic community to develop technologies for space exploration. Moon makes Earth a more livable planet and essential for stable climate. It causes tides, creating a rhythm that has guided humans for thousands of years. It's been always there steadfast revolving around us, evolving with us. The Moon is the only place in the Universe where human beings have set foot on another celestial body beyond Earth. Since the first man walked on the Moon, seeing those images for the first time from another world was inspiring over the next three years. For NASA reaching the moon was just phase one, phase two was hard science. The primary goal was to resolve through observation and sampling some of the unresolved questions about the history of the moon and its relevance to the history of the earth. Rock samples from the Moon landings revolutionized our understanding the Moon; it stunned scientists as they revealed that moon rocks are similar to Earth rocks, and that much of the lunar surface was once covered in molten lava. And being able to have those physical samples was a whole new kind of science that really began as soon as those samples started to come back to Earth. The Apollo missions revealed so much about our moon but when the last mission left in 1972, so many mysteries remain mysteries that we are still trying to uncover, today research focuses on understanding the evolution and composition of the Moon because it has become clear that the Moon holds keys to understanding the origin of Earth and the solar system.

 

 

The Apollo missions of the 1960’s and 1970’s not only inspired millions of people to become scientists and engineers, but the 12 astronauts who landed on the Moon also came home with something far more tangible. Since the “The Eagle has landed”, from 1969 to 1972, there were six Apollo missions which returned to Earth with lunar rocks, core samples, pebbles, sand and dust from the lunar surface. Six Apollo missions collected 2,200 samples of material weighing 381 kilograms (842 pounds) from the moon in a wide range of sizes; some were as large as a football while other samples were as fine as talcum powder. During the same era three robotic Soviet missions landed on the surface of the Moon, these Three Luna spacecraft brought back 301 grams of samples. These missions sampled all kinds of different regions on the Moon, each with their own number of craters. In the run-up to the first moon mission, bringing back lunar samples was not their focus their focus initially. A lot of the people that participated in Apollo were the astronauts, the flight controllers, the engineers. The rocks that astronauts Buzz Aldrin and Neil Armstrong brought back to earth were sent to Houston. The containers were then placed in a vacuum chamber and opened to begin the research process. So later the geologists thought as “we're going to go all the way there, if we had those samples back in our laboratory, we could make measurements you can never make remotely." They helped to train the astronauts in geology. Geology instruction was expanded in subsequent moon missions. Apollo 11 astronauts took nearly 50 pounds of the first array of lunar samples. Apollo 15 was the first one with the rover, so obviously there was the big jump in weight of samples that came back from 15 (169.10 lb) compared to previous missions 11 (47.51 lb),  12 (75.62 lb) and 14 (94.35 lb). The sample mass is even increased in further missions as during Apollo 16 (209.89 lb). Harrison Schmitt, who helped to train previous astronauts, became the first geologist on the moon as part of the Apollo 17 mission in 1972. He spent more than 20 hours on the surface of the moon, collecting samples and extracting soil. And so the Apollo 17 collected (243.40 lb) as Harrison Schmitt was part of Apollo 17, the only scientist/geologist to walk on the moon. Until NASA’s Apollo moon missions, they’d laid on the lunar surface for millions of years undisturbed by humans. The six space flights returned 2200 separate samples from six different exploration sites on the Moon. Nine containers of lunar samples were brought back to Earth. These have been described as the most expensive rocks in the world.

 

 

NASA's Lunar sample laboratory is the facility with collection of seventy percent moon rocks brought back to Earth by astronauts on six of the Apollo missions, humanity's first samples taken from another world are housed at this facility, most in pristine condition. These rocks are older than 99.9% of rocks found on earth, as billions of years of tectonic shift most of the earth's original crust has been melted and recycled. Rocks and soil gathered from the moon missions are housed here in the lunar sample lab, kept pristine to prevent contamination. The lunar sample laboratory facility provides a secure controlled place for the lunar rocks to be stored keeping the lunar samples from being contaminated by earthly materials which is important because these samples are still studied by scientists all over the world. The facility takes extensive measures to prevent contamination of the lunar samples. For example, the facility's storage vaults where the moon rocks stored are elevated above anticipated storm-surge sea level heights to protect the samples from threats posed by hurricanes and tornadoes. Also samples are handled inside the neoprene glove boxes with an additional Teflon glove under very pure nitrogen environment. In the image you can see one of the curators opening the vault door. Each mission has specific designated nitrogen filled cabinets. Nitrogen pumped inside these stainless steel cabinets preserves the rocks inside the display showcases. Even the building material in the lab required extra attention. Special floors and lights were chosen to minimize potential chemical damage to the samples. The collection highlights the lunar rocks pretty much as old as our solar system. This facility was opened in 1979 to house geologic samples returned from the Moon between 1969 and 1972 by the Apollo program missions to the lunar surface.

 

 

The lunar sample laboratory facility at NASA's Johnson space center in Houston Texas is kind of like a library for moon rocks. The life story of the many moon rocks is that about 3.5 billion years ago, molten rock flowed out over the surface of the Moon that cooled into these rock which then got smashed by impacts for about 3.9 billion years, couple million years ago they were loosened up on the Moon surface. Apollo astronauts went to the Moon, picked them up and brought back here on Earth. Since then NASA kept them in cabinet in the lunar sample laboratory facility that later they started to break in a part using band saw and chisels into small pieces for scientists to study. One of the cabinets in the lab in which curators/scientists don’t work as it is purely for display. The nitrogen pumped inside these stainless steel cabinets preserves the rocks, inside this display showcases the collections of the lunar “Rock-stars”. The visitors who actually visit lab have a chance to see some of the really interesting rocks with some really funny and great stories behind them. For example, Apollo 16's rock sample 61016 is the largest rock that was picked up during the Apollo program. It is better known as Big Muley which was named after professor of geology out at University of Texas at Austin, Dr. Bill Muehlberger. The story this rock involves Apollo 16 astronaut Charlie Duke in 1972 and you can see here this is a great picture that shows you exactly how big it was. There is actually a great video on YouTube called Big Muley that you can see the astronaut actually picking it up, Charlie Duke rolling that up the leg of his spacesuit. It was so big that he had to roll it up the side of his leg to get to get a hold of it. Duke shared his experience on collecting this particular rock on the moon that he expressed as “working against the suit”. It was about a football sized sample but now it has been cut with band saw for study purpose, no oils and lubricants are used because that would contaminate the sample. The Apollo missions have sampled the surface in course but also in with rake samples or just scooping up a soil, that was an Apollo 11. This was the last sample collected on the Apollo 11 mission as Neil Armstrong looked the rock box which seemed little empty, so he shoveled some four or five shovelfuls of lunar soil into the rock box. Apollo 11 soil that sits inside two dishes shown in the picture is probably the most valuable sample of the Apollo 11 mission brought back. If we hadn't looked at these soil samples then who knows what would have happened because really important thing that we've learned from this sample was that for the first time we discovered an anorthosite on the Moon. Lunar soil contains fragments of the major lunar rock types: basalt, anorthosite, and breccia. As scientists found few teeny white grains among other majority grains of regolith, these few specks of white stuff is turned out to be an anorthosite (plagioclase feldspar) which they didn’t expect to find there as Apollo 11 landing site, Sea of Tranquility (Mare Tranquillitatis) is one of mare regions of the Moon. Moon rocks fall into two main categories: those found in the lunar highlands (terrae), and those in the maria (mare). The maria regions are composed predominantly of basalt, whereas the highland regions are composed primarily of anorthosite. NASA scientists explanation for that white anorthosite to get to the Sea of Tranquility, it must have been blasted there by a giant impact, like a meteorite, from hundreds of km away in the moon’s highlands.

 

 

Anorthosite on the Moon was again confirmed by the Genesis Rock (sample 15415), it was collected on the Apollo 15 mission. As with bright white color it stood out on the Moon, this is the rock type anorthosite. A rare rock type, the Apollo 15 astronauts were specifically tasked to find a big piece of this anorthosite and they did find it. The Genesis Rock was the first sample of early crustal material to be found on the Moon. It is an anorthosite, a rock composed almost entirely of the mineral anorthite, a type of plagioclase feldspar. The original Genesis rock is about three times as big as the biggest piece in the collection because this is such a popular sample it gets requested a lot and so curators are carving out and giving it away in a lot of pieces for research community. Genesis rock is not obliterated by billions of years of impacts and lava flows it was a key to many mysteries. It was the part of early lunar molten crust created by differences in density, and we find it with differences in color between the Highlands and lowlands. From Earth, lunar anorthosite is visible as the light-colored, highly reflective parts of the Moon's surface known as the lunar highlands. These are the Moon's oldest rocks—more than 4 billion years old—and covered the young Moon's entire surface before its crust was pummeled and broken up by asteroids and comets. Another famous lunar sample from Apollo 15 is Sample 15555, "Great Scott" is both the largest sample returned to Earth from the mission, as well as the most intensively studied of the Apollo 15 rocks. It is named after its collector, Apollo 15 mission commander David Scott. It is medium-grained olivine basalt, with a few percent small vugs. It is probably very close to a liquid composition, i.e., it contains few, if any, accumulated crystals that crystallized approximately 3.3 billion years ago. The term Great Scott was in use as soon as the next mission, Apollo 16, because Charlie Duke used the term just before picking up Big Muley. Big Muley is the largest sample (11.7 kg) returned from the Moon, and Great Scott is the second largest (9.6 kg). Researchers think that the fragment landed on the moon eons ago, when an asteroid hit Earth and blasted pieces of it to the moon when Geologists found the oldest Earth rock ever seen on the Moon which is one of the last places you’d ever suspect. After 500 million years of Moon's formation, this was Hadean eon and the Moon was three times closer to Earth than it is today. It was a bigger target for debris kicked up during impacts with the Earth. At some point, about 4 to 4.1 billion years ago, a region of the Earth cooled down to the point that a rock could actually crystalize about 20 kilometers below the surface. Shortly after that a large asteroid smashed into the Earth and excavated the rock, kicking it into orbit. Eventually it crashed down onto the lunar surface. During Apollo 14 mission Alan Shepard and Edgar Mitchell stepped out onto the lunar surface at the Fra Mauro region of the Moon. They collected rock which is the third largest Moon sample returned during the Apollo program, behind Big Muley and Great Scott. Lunar Sample 14321, better known as "Big Bertha", is a lunar sample containing an embedded Earth-origin meteorite collected on the 1971 Apollo 14 mission. Big Bertha is the first discovered meteorite from Earth, and the embedded meteorite portion is the oldest known Earth rock.

 

 

50 years ago, we studied the lunar sample with the best contemporary technology of the time, but a few untouched samples were locked away so that the scientists of the future, with new methods and new instruments, could learn from those pieces of the Moon what scientists of the 1970’s could not. NASA had the good foresight to keep some of lunar samples unopened because they knew that the technology would evolve at time, and they wanted to keep a few of the moon rocks safe and undisturbed for the next generation of lunar scientists to study. The sample we are talking about is actually a very special sample as it is the lower part of a “double drive tube”, that the astronauts hammered into the ground on the lunar surface. So that tube was filled with rocks and soil, then the lower part of this drive tube was sealed into a vacuum container because it comes from deep within the lunar surface. The idea was to look at different layers on the Moon that might exist underneath the surface, just like geologists on Earth do to see how the surface has changed over time. These tubes get down to a depth of 70 centimeters and so very important means to get a very well preserved sample. Apollo astronauts learned during Apollo 15 mission that down to the depth 70 centimeters you have a minimum temperature zone that's very stable as the ground above it is highly insulating, so at that depth temperature is about minus 20 degrees centigrade which means it's a cold trap. So the volatile elements that are moving around within the soil will tend to concentrate there. After five decades, scientists from the Apollo Next Generation Sample Analysis Program, or ANGSA group looked at a double drive tube of material collected on Apollo 17 by astronaut Gene Cernan that he hammered into the Moon’s ground until the hollow part of the tube filled with rocks and soil.

 

 

Speaking of technological development that NASA was hoping from their next generations to study the Apollo lunar sample; in the year 1903, Marie Skłodowska Curie defended her doctoral thesis on radioactive substances at Université de la Sorbonne in Paris – becoming the first woman in France to receive a doctoral degree in physics. She used her newly discovered element, radium, to be the gamma ray source on x-ray machines. This allowed for more accurate and stronger x-rays. During World War I, she developed radiological cars; mobile radiography units to provide X-ray services to help save the lives of wounded soldiers as electromagnetic radiation of X-rays could help doctors see the bullets embedded in the soldiers as well as locate broken bones. Nowadays X-rays are a form of electromagnetic radiation that not only used for medical imaging, treating cancer but also used for exploring the cosmos. We don’t celebrate 12^th December as Uhuru Satellite day, though it is quite significant date in science and astronomy community as 52 years ago on 12^th December 1970, the first satellite launched specifically for the purpose of X-ray astronomy from the San Marco platform in Kenya. On 9^th December 2021, Imaging X-ray Polarimetry Explorer (IXPE) mission successfully launched into space aboard a SpaceX Falcon 9 rocket. IXPE space observatory is a joint effort of NASA and the Italian Space Agency with three identical telescopes designed to measure the polarization of cosmic X-rays from the most extreme and mysterious objects in the universe like supernova remnants, supermassive black holes, and other such high-energy objects. Exactly after 51 years later of Uhuru X-ray satellite launch anniversary on 13^th December 2021, I encountered the post from ‘Chan Zuckerberg Initiative’ Facebook page showing their X-ray image which is 100,000,000,000 times brighter than an X-ray in a hospital, which was quite surprising for me because it was quite aligned with topic of my posts in the same week (December 2021) that ‘X-ray in Astronomy and Science’.

 

 

The high-energy X-ray regime is the same energy light that doctors and dentists use to study your body, that airport security use to study your luggage; these are very penetrating light that able to go through material. Most of us know that X-rays are commonly used medical diagnostic tool but they can also tell us great deal about astronomical objects. The only difference is that the doctors are sending out X-rays and then studying the X-ray images. Instead, astronomer study some of the most energetic, powerful phenomena in the Universe that create X-rays like supernovae, the sun, black holes, and use that to understand the extreme Universe. The image shows the revolutionary imaging technology with which we can see inside the human organs at unprecedented resolution, unlocking new understanding about health and disease. This is one of the examples of synergy between exploration of the macro and micro world, and how with the advance of technology these two fields are overlapping and could learn a lot from each other because there's a lot of similar procedures and mechanisms that are used in both fields for different outputs. So the innovation towards getting some of these amazing visualizations from deep space in the vast universe is kind of applicable to the microscopic realm as it is also invisible realm. And so while developing devices to capture X-rays from objects in space helped scientists to improve traditional medical equipment involving X-rays.

 

 

When Apollo astronauts began bringing back samples from the moon to earth over 50 years ago NASA chose to keep some samples unopened and untouched. NASA knew that science and technology would evolve and so they wanted future scientists to be able to study these unique samples using new tools and state-of-the-art laboratories. In 2019 almost 50 years later of Apollo mission, the future vision of NASA has become reality with the so-called ANGSA program, which stands for Apollo Next Generation Sample Analysis Program. As today’s technology is better than that was in the 1970’s, this sample gets to be studied by scientists with new technologies and higher precisions to get better data. The Apollo 17 landing site in the Taurus-Littrow Valley was selected so that astronauts could collect samples of the lunar Highlands and investigate the volcanic history of the area. The ANGSA group looked at a tube of material collected on Apollo 17 by astronaut Gene Cernan; hammered a double drive tube into the ground until the hollow part of the tube filled with rocks and soil. Gene Cernan sealed the tube and brought back to Earth, X-rayed, and then stored for decades, until 2019. The hope was that scientists can use this sample to study rock layers to learn about an area’s history. So before actually opening this tube ANGSA team X-rayed it again with a new technology that is called X-ray computed tomography, or short CT scanning, technology that didn't quite exist 50 years ago. Now, back when the tube was first X-rayed, we got the picture of what’s inside. So in the image here you can see at the bottom a picture of the core that was taken in 1974 with an X-ray machine similar to that with doctors use to take X-ray images if you break a bone. Then, in 2019, scientists imaged the sealed tube again with X-ray computed tomography, where a lot of X-ray images from different directions were stitched together into this 3D model. So that’s what the kind of technology improvement NASA hoping from future generation becomes true. Compute Tomography (CT) scanning today is normally used on humans to take 3D pictures of the inside of our bodies in medicine, like taking a picture of your brain without actually cutting us open. And now scientists can use this technology to see what lunar rocks and core tubes look like on the inside without opening them or breaking the rocks. So as the scientists took 3D X-ray CT image of the same moon sample, you can see how much better that picture is and how much more clear it is. So this is an example of how technology evolves over time. This is exactly why NASA had the foresight to keep some of these samples safe and unopened so that the next generation of lunar scientists can now use this technology and learn more things and new things about the moon. So this new technology can also help us identify the inside structure of rocks, as zooming on one of tiny rock that you can see here in the 2019 3D X-ray CT image, the white stripes that you can see here these are minerals that are called “ilmenite” and that tells us  a lot about the chemistry of the moon.

 

 

Scientists studying the moon rocks learnt a great deal about the moon’s development that helped scientists to decide the age of the Moon. It was hoped they would uncover secrets about the Moon but they ended up teaching scientists a lot about the Earth too. Moon rocks fall into two main categories: those found in the lunar highlands, and those in the maria/mare. The two most common kinds are basalts and anorthosites. The lunar basalts, relatively rich in iron and many also in titanium are found in the maria while in the highlands the rocks are largely anorthosites, which are relatively rich in aluminum, calcium, and silicon. In contrast to the Earth, large portions of the lunar crust appear to be composed of rocks with high concentrations of the mineral anorthite. The mare basalts have relatively high iron values. Furthermore, some of the mare basalts have very high levels of titanium (in the form of ilmenite). The Apollo missions in the 1960s and 1970s gave us tremendous insight into the history and structure of the moon. An analysis of the oldest moon rocks show that they are the same age as the oldest rocks found on earth. Also these rocks showed a remarkable similarity to rocks here on Earth. This indicates that they were made at the same place. This indicates that they formed at the same time, these along with many other earth moon system characteristics supports the idea that the Earth Moon combination was the result of a massive collision. Evidence now shows that the Moon was once part of the Earth, and that an impact between the young Earth and another planet in the early Solar System ripped away a huge amount of the Earth’s outer layers which would later cool and re-solidify as the Moon. It was this revelation that led to a game-changing hypothesis called the giant impact theory.

 

 

The moon was likely formed when a Mars-size planet called ‘Theia’ hit Earth and blew parts of the planet into space. The giant impact theory says that in the early age of our solar system there were lots of clueless planetary bodies traveling around and on one fateful day around 4.5 billion years ago something as big as mars crashed into earth who was still a baby at the time. This collision created a lot of molten planetary debris but because of earth gravity it didn't all drift away into space instead it started orbiting around earth. The collision would have tilted the earth liquefied vaporized and homogenized the mantles of the two planets and ejected massive amounts of matter into space and eventually came together where it coalesced into forming the moon. This process is called accretion; the key reason for this scenario is the similarity between rocks from Earth and the moon. At that stage the moon was still a huge ball of molten rock which geologists refer to as magma and over time things started to cool down and a solid core mostly made of iron alloy was formed and after that more minerals started to crystallize and sink to the bottom forming a layer which we call the mantle. Because of the high temperature and pressure the materials at this layer are actually not in the solid state still molten, these minerals mostly olivine and pyroxene are heavier and darker in color. The remaining materials mostly made of plagioclase feldspar floated to the surface cooled down last and solidified over time forming the crust of the moon.  This layer is the light colored part of the main surface that we see today. This is called the lunar magma ocean theory and it is the leading explanation of the moon's early evolution. The homogenized mantle would have been completely magma, thus the rocks that formed from this magma will be the oldest rocks on the Earth and the same would hold true for the Moon. Determining the age of rocks is called geochronology but before the early 20^th century there was no way to do it.

 

 

In 1895, Wilhelm Röntgen discovered the existence of X-rays. In 1896, Henri Becquerel discovered that uranium spontaneously emitted a mysterious radiation that could interact with photographic film and resembled X-rays in their penetrating power. He demonstrated that this radiation, unlike phosphorescence, did not depend on an external source of energy but seemed to arise spontaneously from uranium itself. The uranium salts caused a blackening of the plate in spite of the plate being wrapped in black paper. These radiations were given the name "Becquerel Rays". It became clear from these experiments that there was a form of invisible radiation that could pass through paper and was causing the plate to react as if exposed to light. They were rare places in the world where rocks rich in uranium possessed these strange properties inspired Marie on her scientific quest and so influenced by Becquerel’s important discoveries, Curie decided to look into uranium rays as a possible field of research for a thesis. Marie Curie along with her husband and research partner Pierre wanted to know how a piece of matter could make it possible to see through skin and even walls. So the discovery of this invisible radiation by Henri Becquerel in 1896 while working with phosphorescent materials which eventually would get dubbed as “radioactivity” by Marie and Pierre Curie as they went on to study radioactivity in great detail than ever before. Curie soon found that the element thorium emitted similar radiation. In 1898, Marie and Pierre had discovered completely new elements, polonium named for Marie's native Poland, and radium, the Latin word for ray.

 

 

In 1927, two physicists Ellis and Wooster firmly established that the energy spectrum of electrons emitted in β decay was continuous. They set out to measure this energy they use bismuth 210 a product of radium decay that itself decays into polonium. The rate at which unstable radioactive nuclei decay is called the activity of that sample. The greater is the activity (decay rate), the more nuclear decays per second. Both the activity rate and the number of radioactive nuclei vary over time as a sample decays the number of radioactive nuclei decreases and with fewer radioactive nuclei the activity rate also decreases, from this we get the exponential law of radioactive decay that tells us how the number of radioactive decay in a sample decreases with time. The half-life is the time taken for the activity of a given amount of a radioactive substance to decay to half of its initial value. Bismuth 210 has a half-life of five days meaning it takes five days for half of its any amount to transform into polonium. How do we use this to get the age of something? And the answer is a technique called radiometric dating which lets us tell the age of certain types of rock. In the 1920s a British geologist named Arthur Holmes the father of modern geochronology came up with an accurate method called radiometric dating, he performed first uranium-lead dating. Radiometric dating or radioactive dating or radioisotope dating is a technique which is used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed. It relies on the fact that certain elements have what are called isotopes where separate atoms of the same element differ in the number of neutrons in a nucleus but have the same number of protons. These different versions of the atom with extra neutrons in them, each radioactive isotope decays at a consistent rate. For example, there are two isotopes of uranium with masses 238 and 235, each of them are radioactive and decays at a separate rate to a separate isotope of lead. Uranium-235 decay to lead-207 with a half-life of about 700 million years, and one based on uranium-238 decay to lead-206 with a half-life of about 4.5 billion years, so it can be used to date things as old as a solar system itself.

 

 

The radiometric dating methods are used in geochronology to establish the geologic time scale. The method compares the abundance of a naturally occurring radioactive isotope within the material to the abundance of its decay products, which form at a known constant rate of decay. These measurements give us something we already mentioned above in this blog called the half-life or the amount of time it takes for one half of the isotope to decay, so when an isotopes half-life is up half your original element will be gone transformed into a different isotope another half-life and you're down to a quarter of your original amount a half-life after that and you're down to an eighth and so on. Among the best-known radiometric dating techniques are radiocarbon dating, potassium–argon dating and uranium–lead dating. The length of a half-life is different for every isotope, if you wait for enough half-lives to pass then you will have a hard time detecting any of your original material. So to date something relatively recent you want an isotope that decays quickly to go older you want an isotope that decays very slowly. The radiocarbon dating uses carbon-14 which has a half-life of 5730 years, to date things that are older than that we use an isotope that decays very slowly. The half-lives of radioactive atoms have a huge range; from nearly instantaneous as less than a zeptosecond to far longer than the age of the universe. This is rather easily measured with devices like a Geiger counter given the number of radiating molecules in a sample and measuring the activity we can calculate the probability for any one molecule to decay in a second this is called decay constant. Radioactive decay is a stochastic (i.e. random) process at the level of single atoms. According to quantum theory, it is impossible to predict when a particular atom will decay, regardless of how long the atom has existed. However, for a significant number of identical atoms, the overall decay rate can be expressed as decay constant or as half-life. The decay constant is always a small number constant over time and different for different materials. So because the radioactive decay process is not thought to vary significantly in mechanism over time, it is a valuable tool in estimating the absolute ages of certain materials.

 

 

How does the geologist know that the earth is 4.5 billion years old? Some atoms in the rock could be radioactive which means they spontaneously disintegrate and become other elements. The radiometric dating method requires that the rock contain at least some measurable amount of radioactive materials such as uranium and the lead it decays into to understand how we can use the uranium to date rock. For geological materials, the radioisotopes and some of their decay products become trapped when a rock solidifies, and can then later be used to estimate the date of the solidification. Uranium–lead dating is often performed on the mineral zircon. The radioisotopes do not decay directly into a stable state; rather they go through stages of radioactive decay until reaching a stable isotope. The unstable radioactive element like uranium atom becomes a thorium atom. On average, it takes a few billion years and then in less than months unstable thorium turns into protactinium. A minute later, protactinium becomes something else and likewise these atoms undergoes ten more nuclear transmutations until it reaches the last stop on the decay chain which is a stable atom of lead and it will remain for eternity. The nuclei of the radioactive substances are generally unstable and can undergo an internal change ejecting particles and electromagnetic radiation. Lead, atomic number 82, is the heaviest element to have any isotopes stable (to the limit of measurement) to radioactive decay. The reason behind Madame Curie's remains interred in a lead-lined coffin, keeping the radiation that was the heart of her research, and likely the cause of her death, well contained. Radioactive decay is seen in all isotopes of all elements of atomic number 83 (bismuth) or greater, these elements were observed to emit such radiations. In the 20^th century there was a huge effort, lasting decades to measure the time it takes for each radioactive element to transmute into another element. Physicists discovered that the atoms of each unstable element decay at a constant rate. The unstable radioactive element like Uranium that we use is called the parent and the stable isotope like Lead that we end up with is called the daughter. Radiometric dating only works if the only source of the daughter isotope is the decay of the parent isotope. So we need a rock that behaves a bit like a sealed time capsule preventing daughter isotopes from leaving and keeping any new foreign parent isotopes away. Zircon contains a little bit of uranium but no lead and so we can actually measure the uranium decay chain and measure lead which the uranium decays to; so that lead over uranium is actually a chronometer. Uranium-lead is one of the premier geochronometers; we can cover the full range of geological time going from 4.56 billion years ago which is the age of the solar system by dating zircons from meteorites all the way through to about a million years or even less when they start looking at very young rocks such as some of the very young volcanic rocks on Earth. So we can actually solve the equations of radioactive decay and come up with an age of a specific zircon.

 

 

The tiny zircon crystals which would fit comfortably on the pinhead are excellent time capsules, tight as a drum and tough. Nothing gets in or out of them, even for billions of years. Zircon crystals can trap radioactive uranium inside them as well as its daughter isotope lead. Each little zircon has only a few parts per million of uranium inside that decays into even tinier amounts of lead and can be dated using modern analytical techniques. So measure the proportion of uranium to lead in a zircon crystal and you can figure out when it must have formed. So that is what's revolutionary about this idea of looking for zircons because these little time capsules are information that represents a fascinating window onto the very tumultuous time in the history of our planet; very earliest evolution of the earth. Originally formed by crystallization from magma or in metamorphic rocks, zircons are so durable and resistant to chemical attack that they rarely go away. So as a survivor zircon is one of Earth's longest-running and most accurate minerals used for dating that gives us the insight back through these processes that destroy our all other minerals. They are very hard, very resistant to pressure and temperature changes, very resistant to melting and so may survive many geologic events, which can be recorded in rings of additional zircon that grow around the original crystal like tree rings. Zircon is chemically (inert) stable and is not disturbed during weathering, most importantly for our purposes that single grains of zircon with a diameter about the thickness of a human hair incorporates uranium at the time it crystallizes, which over time decays to lead that is available for analysis in the today’s most advanced laboratories. When we find a rock that incorporates zircon, we can date these zircons that have been forming since the earth was only about 200 million years old which allows us to understand processes that have happened during the evolution of the early earth. When we see images of the zircon grains using the scanning electron microscope that survived eons of pressure heat and tectonic shift giving us an idea of what earth was like three to four billion years ago. The geological events leaves a ring in the zircon as more material grows over top kind of like rings in a tree and each ring has a story to tell with the rings closer to the center reaching even further back in time. So it's like growth rings on a tree; the inner part is older than the outer as they grow from inside to outside formed from the events a few hundred or even a billion years apart. So we’ve got over a billion years of history represented within a single zircon grain with the amount of uranium-lead geochronology information that represents the age.

 

 

The earliest earth was an incredibly tumultuous place, the planet has just been assembled and maybe there were unassembled planets slamming into the earth. We call this the Hadean eon (about 20 to 100 million years after the Solar System coalesced) which was widely believed to have been literally what that term means that is hell on earth originated from Greek word ‘hades’. The only surviving samples we have from the hadean eon; the very earliest period of our planet's history is ancient zircons from the jack hills, a range of hills in Midwest of Western Australia that’s about eight hundred kilometers north of Perth. During the hadean eon the outer surface of the earth was a magma ocean with thousands of degrees Celsius hot. In January 2001 nature published an article on Curtin University study of the zircon crystals from Jack Hills in Midwest Western Australia zircon, using uranium lead zircon analysis following standard operating techniques. They found the oldest solid earth crust matter ever discovered at 4.356 billion years old. At the end of the first Apollo 14 EVA (extravehicular activity) a large soil sample was collected from the area near the lander, the bulk of the soil sample was scooped from a small crater. The sample was chosen as one of the reference soils for the lunar Highlands, scientists used a chemical abrasion isotope dilution thermal ionization mass spectrometry analysis on zircon crystals in the sample which is the same process we use for our earth rocks analysis. By the time of the Apollo sample returns, scientists had refined this art, and, using meteorite samples, they were already investigating the early history of the solar system. At only about width of a human hair across, though these crystals are not considered rocks, but rather chips off older blocks, making them the oldest fragments of Earth, a 2014 paper used atom-probe tomography and confirmed age of Jack Hills Zircon crystal to be 4.374 billion years old. The moon zircon crystal from Apollo 14 was found to be 4.3 billion years old. This is quite close to the oldest Earth Rock indicating that they formed at the same time as the oldest rocks on Earth. These findings constitute significant support to the giant impact hypothesis but the giant impact idea remains a hypothesis and dating methods are evolving, different dating methods indicate different ages for moon rocks. The search for rocks on earth continues and another trip to the moon could change our view completely. But for now in early 2020, the general scientific consensus is that the current version of the earth is at least 4.3 billion years old and the moon is close to the same age as the Earth. So Earth's moon is some 4.47 billion years old, its birthday having come about 95 million years after the formation of the solar system. This means Earth's closest companion is some 60 million years younger than previously estimated.

 

 

 “Big Bertha” was one of the moon rocks brought back by the Apollo 14 crew for geological analysis. Apollo 14 was the third mission to land on the surface of the Moon, setting down in the Fra Mauro highlands. The task of Apollo astronauts was to collect samples from surrounding craters because the forces that make craters, blast ancient rocks to the surface. They had a special collapsible cart called the modular equipment transporter to carry tools and lunar samples. So the Apollo 14 crew Shepard and Mitchell were collecting the biggest payload relative to their previous succeeding Apollo missions, 92 pounds (42 kilograms) of Moon rocks and soil, which could help scientists in determining the forces that might have shaped the Moon and Earth. Almost 50 years after those samples were brought back to Earth, Geologists from the Center for Lunar Science and Exploration developed techniques that allowed them to identify impactor fragments mixed in with the churned up lunar regolith. They realized this would allow them to find rocks that might have originated on Earth. The research team — led by Research Scientist Jeremy Bellucci, of the Swedish Museum of Natural History, and Professor Alexander Nemchin, of the Swedish Museum and Curtin University in Australia — analyzed lunar samples collected by members of the Apollo 14 mission, which explored the lunar surface for a few days in early February 1971. Among their samples was a stunning find; one very special sample, a rock that had been formed here on Earth. They discovered a bit of oldest Earth rock from about 4 billion years ago—on the Moon. A moon rock brought back from the lunar surface by Apollo 14 astronauts in 1971 harbors a tiny piece of the ancient Earth (the "felsite clast" identified by the arrow). They found that one rock contained a 2-gram fragment composed of quartz, feldspar and zircon, all of which are extremely rare lunar minerals but very common here on Earth. Chemical analyses indicated that the fragment crystallized or cooled into a rock in a terrestrial-like oxidized environment, at temperatures consistent with those found in the near subsurface of the early Earth rather than being a native Moon rock. The available evidence suggests that the fragment crystallized 4.1 billion to 4 billion years ago about 12 miles (20 kilometers) beneath Earth's surface, then this felsite may have been blasted off our planet to our planet’s satellite by a powerful impact event shortly thereafter. This could be the first evidence that rocks can be chipped off Earth and land elsewhere. The Moon rock dubbed Big Bertha contains an Earth fragment is one of the oldest Earth rocks ever discovered, here or elsewhere.  So when the Apollo 14 astronauts returned their lunar samples back to Earth, they were carrying one rock that had formed on Earth 4 to 4.1 billion years ago, which was carved out of our planet during the time of intense bombardment and delivered to the Moon. The sample is therefore a relic of an intense period of bombardment that shaped the solar system during the first billion years. This is known as the Hadean era, a time that begins with the Earth’s formation in the solar nebula 4.6 billion years ago, and ends about 4 billion years ago. After that period, the Moon was affected by some impact events and so another large impact that happened on the Moon about 3.9 billion years ago partially melting this Earth rock on the Moon combining it with other lunar material. The rock was thus subsequently mixed with other lunar surface materials into one sample referred as breccia rock. The study about this possible relic from the Hadean Earth, published online on 24th January 2019 in the journal Earth and Planetary Science Letters that tells us that over a 4 billion year old chunk of felsite that was collected during the Apollo 14 mission in 1971.

 

 

Studying the moon is not just an abstract thought we're really trying to understand ourselves where we come from? How did earth form? When we have stations on the moon with geologists exploring roving the surface collecting more moon samples and more rocks, we're going to find fragments of the most ancient earth meteorites that landed on the moon. It will tell us about our earliest history how the oceans formed, how the atmosphere formed, whether there was a life in those earliest times. Today Moon orbits Earth at an average distance of 238,855 miles (384,400 kilometers) which means 30 Earth-sized planets could fit in between Earth and the Moon. But we know the Moon is slowly drifting away from the Earth at a rate of by about 4 centimeters per year. If we run the clock backwards almost 4 billion years ago, during the Hadean period of heavy bombardment when the Moon was three times closer to Earth than it is today; only about 80,000 miles (134,000 kilometers) away which means the Moon was orbiting about 20 Earth radii distant or 10 Earth diameters away. Which means the Moon was 2.8 times larger in the sky, one of these ancient asteroid impacts had no problem digging up Earth rock that was formed 20 km below the surface and kicking it into a region that overlapped the Moon’s orbit. The oldest rock ever found on Earth date back to about 3.8 billion years, and matches this idea of a mostly molten Earth surface. This date could be found in many of the oldest-known rocks from around the world, and appeared to represent a strong "cutoff point" beyond which older rocks could not be found, which defined the boundary between the earlier Hadean and later Archean eons as biologists generally believe that life got a foothold on Earth between 4.1 and 3.8 billion years ago. During the earliest time, the entire Earth was molten rock, but then over 800 million years it eventually cooled down to the point that solid rocks could actually form on the surface. This is when the geological age of the Earth could actually begin. These dates remained fairly constant even across various dating methods, including the system considered the most accurate and least affected by environment, uranium–lead dating of zircons. It is an excellent research that highlights the Hadean Earth and the bombardment that modified our planet during the dawn of life.

 

 

The Late Heavy Bombardment (LHB) or the lunar cataclysm is a theory that the Earth, and the entire inner solar system, suffered through an intense spike in asteroid bombardment roughly 4 billion years ago. Before the formulation of the LHB hypothesis, geologists generally assumed that Earth remained molten until about 3.8 billion years. Today Earth is a beautiful planet with oceans and continents, barely an impact crater to be seen. But 3.9 billion years ago, when the Solar System was still filled with debris left over from planetary formation. Around this time, from 4.1 to 3.8 billion years ago was a period known as the late heavy bombardment (LHB). It was a “heavy bombardment” that created the largest impact basins on the Moon, Mars, and Mercury. This was a time when the giant planets in the Solar System were shifting around their orbits. The mass of impacting material increased by a factor of about 1000 compared to times shortly before. Four billion years ago, the inner solar system apparently experienced an unexpectedly large number of meteor collisions that scientists typically call the late heavy bombardment (LHB). Over 4.5 billion years ago, the planets in our solar system formed, so this was over 500 million years after the sun and planets had formed. Evidence for the LHB derived from rock samples of Moon craters brought back by the Apollo astronauts. Many of these famous samples from the moon were of rocks that had been deformed or created by melting during large impacts these crystalline melt rocks could not have formed without large impacts tens to hundreds of kilometers in extent. Isotopic dating showed that these rocks were last molten during impact events in a rather narrow interval of time, suggesting that a large proportion of craters were formed during this period. It is quite surprising that the ages of those melt rocks all clustered between about 3.8 and 4 billion years ago. This suggested that several large impacts occurred on the moon during a concentrated time period of 200 million years. One of the implications from the famous Apollo moon rocks that not so widely appreciated, the giant planets changed their distance from the sun. The Apollo rocks helped solve this question to a point because many lunar samples were dated to 3.9 billion years ago; study suggests that their radioactive ages could have been set by LHB caused due to “giant planet migration”.

 

 

 

Why and how scientists think that “giant planet migration” is the reason behind “late heavy bombardment”? Analysis of the moon samples seems to imply that a significant percentage of the lunar impact basins formed within a very short period of time between about 4 and 3.85 billion years ago. Several hypotheses attempt to explain this apparent spike in the flux of impactors in the inner Solar System, but no consensus yet exists. Scientist thinks that if there was a big increase in the number of impacts then perhaps there was also a big but more temporary disturbance, something big that perturbed a much larger number of impactors inwards from the asteroid belt and Kuiper belt. If we want a big disturbance then the biggest planets especially Jupiter is the natural place to look. Computer simulations allow us to study how the giant planets formed and gravitationally interacted early in the solar system. In the Nice model which is quite popular among planetary scientists, postulates that the Late Heavy Bombardment is the result of a dynamical instability in the outer Solar System. In the model giant planets underwent orbital migration causing resonances to sweep through the asteroid belt, Kuiper belt which resulted in scattering of asteroids and comets from these belts into eccentric orbits until they enter the inner Solar System and impact the terrestrial planets. Jupiter migrated inward; Saturn migrated outward until Jupiter and Saturn end up in a very special configuration that the alignment between the planets reached an almost perfect two to one orbit-orbit resonance. As Jupiter was moving inwards its orbital period kept on decreasing and as Saturn's orbit was moving outwards its orbital period kept on increasing eventually they reach a state where Jupiter completes exactly two whole orbits every time Saturn completes one. This flung Uranus and Neptune outward and ejected asteroids out of the belt. This "migration" is a stage in the solar system evolution when the largest planets started to move away from the sun. That so many gas giants, which form in the outer regions of their system, end up so close to their stars suggests that gas giants migrate and that such migration may have happened in the solar system’s history. According to the Grand Tack hypothesis, Jupiter may have done so within a few million years of the solar system’s formation. It is "a concept wherein Jupiter gravitationally affects the orbits of the outer planets Saturn, Uranus and Neptune. The present-day structure of the Asteroid Belt is crucial observational evidence for Planetary Migration. Numerical simulations show that the Asteroid belt could have attained its present form only if the Jovian planets migrated.

 

 

Planetary migration occurs because once a planet has formed; it interacts with a protoplanetary disk of gas or planetesimals resulting in the alteration of its orbital radius due to gravitational forces between the planet and material in the disk. How scientists think that “giant planet migration” is even possible? Answer is Exoplanets. In the 1990s astronomers confirmed that other stars have one or more planets revolving around them. Studies of these extrasolar planetary systems have both supported and challenged astronomers’ theoretical models of how Earth’s solar system formed. Unlike the solar system, many extrasolar planetary systems have large gas giants like Jupiter orbiting very close to their stars, and in some cases these “hot Jupiters” are closer to their star than Mercury is to the Sun. There are simulations that demonstrate the giant planets can change their orbits somewhat during their formation. This idea that giant planets migrate was a huge surprise but the idea makes more sense after studying thousands of exoplanets orbiting other stars. Sometimes those gas giant planets migrate very close to their parent stars; planetary migration is the most likely explanation for exoplanets with Jovian masses but orbits of only a few days. In this way, planets can migrate from their original location, a phenomenon that can explain the diversity of exoplanets (an Exoplanet is a planet outside our Solar System). As in the Nice model, systems of exoplanets with an outer disk of planetesimals can also undergo similar dynamical instabilities following resonance crossings during planetesimal-driven migration; the dissipation of the gas disk due to such instabilities alter their orbits and in some cases result in planets being ejected or colliding with the star. Not so long ago, we lived in a universe with only a small number of known planets, all of them orbiting our Sun. In late 1990, exoplanets weren't really a thing, maybe there were like one or two discoveries at that time and now there are thousands of them, they are all the rage. In January 1992, first exoplanet was discovered, 30 years later in 2022 the count of confirmed exoplanets ticked past the 5,000 mark. Although planetary migration is expected to lead to systems with chains of resonant planets most exoplanets are not in resonances. The resonance chains can be disrupted by gravitational instabilities once the gas disk dissipates. Interactions with leftover planetesimals can break resonances of low mass planets leaving them in orbits slightly outside the resonance. In our solar system, in contrast to the outer planets, the inner planets are not believed to have migrated significantly over the age of the Solar System, because their orbits have remained stable following the period of giant impacts.

 

 

Scientists studying the rocks learnt a great deal about the many impacts early in the Moon’s development. These created huge craters some the size of large countries Ancient volcanic eruptions then filled some of these basins with vast plains of lava creating the dry seas that can be seen by humans on Earth. The cause for the eruption of mare basalts has one explanation that suggests large meteorites were hitting the Moon in its early history leaving large craters which then were filled with lava. All lunar samples have stories, so the trick is trying to read the story. For instance, when one lava flow is covering another that tells you that the top lava flow is younger. And both lava flows must be younger than whatever was under them. The majority of these lava deposits erupted or flowed into the depressions associated with impact basins. The near side of the Moon is marked by dark volcanic maria ("seas"), which fill the spaces between bright ancient crustal highlands and prominent impact craters. The most distinctive aspect of the Moon is the contrast between its bright and dark zones. The highlands are anorthositic in composition, whereas the maria are basaltic. Many volcanic eruptions occurred on the Moon’s surface over its geological history, forming large sheets of basaltic rock. These can be seen as darker regions / dark patches looking up at the Moon. In the past when people looked up at the moon and they saw these darker regions and they thought these are seas on the moon which is why we call these regions as Mare or Maria (Latin for Sea) because they look like oceans but actually are vast plains of volcanic lava while the original crust being higher in elevation. The lighter-colored crust regions of the Moon are called terrae, or more commonly highlands, because they are higher than most maria regions. The maria often coincide with the "lowlands," but it is important to note that the lowlands; the lowest elevations of the Moon within the far side South Pole-Aitken basin are only modestly covered by mare. Almost all maria are on the near side of the Moon, and cover 31% of the surface of the near side compared with 2% of the far side. The concentration of maria on the near side likely reflects the substantially thicker crust of the highlands of the Far Side. I wondered perhaps Moon’s tidal locking with the Earth has something to do with it. And yes some scientists think it may be a consequence of asymmetrical tidal heating when the Moon was much closer to the Earth. Just like on Earth, different parts of the Moon’s surface formed at different times. Some areas probably date all the way back to the early days of the Solar System, while others formed in the eons since. Most of the large impact basins and Moon's mare basalts erupted during the Imbrian period, 3.3–3.8 billion years ago. So a large portion of the mare formed, or flowed into, the low elevations associated with the nearside impact basins and represents ancient flood basaltic eruptions. However, the youngest lavas erupted within Oceanus Procellarum and do not correspond to any known impact structure. If you want to piece together a rough history of the Moon, all you really need is a telescope and a method called relative dating, which despite the name has nothing to do with incest. Basically, you figure out how old things are by comparing them to each other. For instance, when one lava flow is covering another that tells you that the top lava flow is younger. And both lava flows must be younger than craters under them. But if you want to know how many years ago those events happened, you need to switch to an absolute dating system. The maria are clearly younger than the surrounding highlands given their lower density of impact craters. The highlands are older than the visible maria, and hence are more heavily cratered. They have been radiometrically dated to having formed 4.4 billion years ago, and may represent plagioclase cumulates of the lunar magma ocean.

 

 

When NASA’s New Horizons probe flew by Pluto, it captured amazing picture of an enormous icy plain in the shape of a heart. Six months later, we learned that the heart was no more than ten million years old, which is like yesterday compared to Pluto’s four and a half billion year history. What’s even more amazing is that we only know this because astronauts brought a bunch of rocks home from the Moon almost fifty years ago. In fact, any time we’ve figured out the age of a surface in the Solar System, it’s thanks to those moon rocks. Crater counting is a method or perhaps the principal tool used by astrogeologists for estimating the surface ages of planets, their moons and even large asteroids throughout the solar system. It is based upon the assumptions that when a piece of planetary surface is new, then it has no impact craters; impact craters accumulate after that at a rate that is assumed known. The method has been calibrated using the ages obtained by radiometric dating of samples returned from the Moon by the Luna and Apollo missions. Until now, the technique has relied on scientist’s painstakingly identifying and counting impact craters by hand. The density of impact craters on a planetary surface can be used as a measure of the age of that surface. Surfaces with relatively few craters are young, while surfaces with many craters are old. Consequently, counting how many craters of various sizes there are in a given area allows determining how long they have accumulated and, consequently, how long ago the surface has formed. The Moon is covered in impact craters; one of the main uses of craters is to tell ages. Each crater, individually, can tell a story, both about the surface it impacted into and about the incoming meteor. On the moon, we have a chronology that tells us that a surface that has a certain number of craters of a certain size will be a specific age. The basic idea is that if a surface has been around longer (it's older), it will have accumulated more craters. Therefore all the craters together can tell stories about the history of the surface and the history of solar system bombardment. But when scientists used crater counting method to estimate the age of Pluto’s heart, they had to make assumptions about how the rate of impacts on Pluto compared to the rate on the Moon. Another issue is that crater counting doesn’t seem to work for surfaces that are more than about four billion years old. At that point, the surface reaches saturation, meaning that it has so many craters that each new crater just obliterates an old one.

 

 

Lunar samples provided ages for some of the large impact basins that we see on the near side like the Imbrium, Nectaris and Serenitatis basins. The ages of the large impact basins were somewhat more spread out from about 4.2 billion to about 3.7 billion years old. So there's some uncertainty about how to describe the duration of bombardment but the evidence seems strong that there were a lot more impacts and much larger impacts around this time compared to earlier or later times. Some supporting evidence also comes from craters on Mercury and Mars plus meteorites that have landed on earth but based primarily on Moon rocks the evidence points to a spike in the number of impacts around four billion years ago. The main piece of evidence for a lunar cataclysm or late heavy bombardment comes from the radiometric ages of impact-melted rocks collected during the Apollo missions. The majority of these impact melts are thought to have formed during the collision of asteroids or comets tens of kilometers across, forming impact craters hundreds of kilometers in diameter. The Apollo 15, 16, and 17 landing sites were chosen as a result of their proximity to the Imbrium, Nectaris, and Serenitatis basins, respectively. The apparent clustering of ages of these impact melts, between about 3.8 and 4.1 billion years, led to postulation that the ages record an intense bombardment of the Moon. The Nice model opens our eyes to possibilities that the orbits of the giant planets dance around the solar system as the giants migrate and the model is able to explain some previously taken for granted features we see in the solar system. But we don't know for sure that the model describes what actually happened, even the late heavy bombardment which is one of the major consequences that made the Nice model so attractive may not be real that's because there is some debate over evidence from the moon rocks supporting the claim that there was a spike in large impacts around 4 billion years ago. It is now recognized that ejecta from the Imbrium impact basin (one of the youngest large impact basins on the Moon) should be found at all of the Apollo landing sites. The debate stems from looking at the locations where we got our lunar samples during the Apollo missions; after all it was these lunar samples that provided the first and strongest evidence that a late heavy series of large impacts occurred in a relatively short geologic time. But some scientists think it's also possible that all of these moon rock samples can be actually sampling from just one very large impact crater on the moon; Imbrium, that's not because we collected all the samples from a single location but because the Imbrium impact would have spread ejecta over large distances surrounding the basin and since Imbrium is the youngest of the large impact basins, the ejecta would have landed on top. At the time, the hypothesis was considered controversial. Could it be possible that samples we collected from six different locations on the moon all happened to be ejected from Imbrium? If so that would explain but a very different way while the ages in the samples cluster around the age of Imbrium and so all those impacts still may happened but no so close together in time, instead it may be that there was a more steady and less dramatic flux of impactors from the beginning of the solar system around 4.5 billion years ago down to about 3.5 billion years ago without a spike centered at 4 billion years ago. And the fact that we don't see a lot of impact-melted crystals older than about 4.2 billion years; maybe simply because older material was more likely to be pulverized by later impacts. Perhaps virtually all the older evidence has been destroyed, so which is it? Was there a concentrated bombardment caused by the giant planets migration? Or was it not? Perhaps the most important thing that will help is more moon samples from a wider variety of its locations and different impact basins. After all the ages of surface features on Mars, Mercury and Venus are anchored to ages of craters determined from lunar samples combined with counting and comparing the relative number of craters on each world. If more samples from the moon resulted in a correction to the surface ages previously determined for lunar features that would cause to revise the timing and sequence of events throughout the inner solar system. The timing of events early in the solar system may be fundamentally changed by better knowledge of lunar impact basins.

 

 

Apollo 11 man's first landing on the moon there was no objective more important to science than the collection and return of samples of the lunar surface as never before we had the opportunity to examine extraterrestrial material from a positively known location and context fortunately at the site of the landing in the southwestern part of the Sea of Tranquility. There was a considerable variety of lunar material much of it debris from nearby impact craters. Outside the Lunar Module named Eagle, when Neil Armstrong was getting ready to seal up the rock box before doing that he decided to do shovel the moon sample to put inside rock box, so he scooped up the sandy stuff and then sealed it up. The soil sits inside these two dishes is the last sample collected on Apollo 11. It was the largest single sample of brought back from Apollo 11 and it turned out being the most valuable sample that Apollo 11 mission brought back to Earth because as people looked through it, they found little fragments of white rock. Back in the 1960s, even though scientists had figured out enough science to put people on the moon, it still murky for them that how it had formed and so before Apollo 11 we really didn't understand how the moon formed. So one of the big things that scientists learned from Apollo 11 soil samples when they were discovered these white anorthosite grains, the only way to explain their existence or their formation is that the moon at some point must have been fully molten. As big gigantic magma ball in space and the only way to do that is that you have to have a gigantic impact between two protoplanets that then made a lot of like debris cloud the inner parts then formed earth and then the debris part that went around it coalesced to form the moon. So that how sparked the idea of the giant impact and the magma ocean for the moon.

 

 

The existence of the magma ocean phase was first recognized from small fragments in the Apollo 11 samples, but Apollo 15's Genesis Rock is important because it is much larger than any previous sample of lunar anorthosite. One of the most famous moon rocks is the Genesis Rock (sample 15415), the first sample of early crustal material to be found on the Moon. It is a sample of Moon rock retrieved by Apollo 15 astronauts James Irwin and David Scott in 1971 during their second lunar extra vehicular activity (EVA) at Spur crater. It was the only anorthosite that they found and is currently stored at the Lunar Sample Laboratory Facility in Houston, Texas. In fact, the Apollo 15 site was selected in part to find such a rock. Chemical analysis of the Genesis Rock indicated it is an anorthosite, composed mostly of a type of plagioclase feldspar known as anorthite mineral. The rock was formed in the early stages of the Solar System, at least 4 billion years ago. It nicknamed as the Genesis rock because it stands as a major clue in unraveling the formative processes of the Moon and the Earth. It told us how the moon formed and how it evolved for the first couple hundred million years. Genesis rock allowed scientists to unlock how the moon formed supporting giant impact hypothesis, as the dating of pyroxenes from other lunar anorthosite samples gave a samarium–neodymium age of crystallization of 4.46 billion years. Moon samples indicate that the Moon was once molten down to a substantial, but unknown depth. This might have required more energy than predicted to be available from the accretion of a body of the Moon's size. An extremely energetic process, such as a giant impact, could provide this energy.

 

 

The identification of anorthositic mineral fragments in Apollo 11 moon sample led to the bold hypothesis that a large portion of the Moon was once molten, and that the crust formed by fractional crystallization of this magma ocean. Also from studying our own planet Earth we know anorthosite forms in a very special way. Almost all the rocks at the lunar surface are igneous which means they are formed from the cooling of lava or magma. (By contrast, the most prevalent rocks exposed on Earth’s surface are sedimentary, which required the action of water or wind for their formation.) As magma cools and crystallizes, anorthosite floats to the top because of its less density than other stuff in the magma. Just like how as ice solidifies out of liquid water, it floats because it’s less dense. So for the moon’s surface to be covered in white anorthosites, whole moon must have melted at some point. The giant impact hypothesis is one explanation, Earth gets smacked by another Mars-sized planet and then melted cloud of debris condenses into our moon, creating a thousand-km-thick ocean of magma. Also team of scientists analyzed over 30 moon rock samples across 15 rock types from Apollo missions fit on a terrestrial fractionation line. The signature detail was that oxygen isotopes sealed in Moon rocks — the “flavors” of oxygen atoms — matched those on Earth. Ultimately, they revealed Apollo's biggest story, the origin of the Moon itself. The most striking analytical finding showed the samples are eerily similar to Earth rocks in several ways. The Moon's oxygen isotopic ratios are essentially identical to those of Earth. As these rocks showed a remarkable similarity to rocks here on Earth that indicates they were made at the same place and so indirect evidence for the giant impact scenario came from this study of moon rocks collected during the Apollo Moon landings.

 

 

There are some theories to explain the formation of the moon. Before the Apollo landings, there was popular idea about how we got the Moon that it was captured like Neptune’s moon Triton or Pluto’s moon Charon. But studying the moon rocks the astronauts brought back basically ruled out that possibility as the researchers found that chemical signatures in those samples matched rocks on Earth almost exactly, which would be super unlikely if the Moon was captured from somewhere else in the Solar System. The Moon is a piece of Earth as it has the same elements, the same isotopes, the same minerals as Earth. Hence currently the most popular explanation is the giant impact theory. Because there were plenty of questions like why the Earth and moon are made of the same elements and atomic isotopes, or why the moon has slowly been moving farther away from Earth for billions of years, or why the moon’s core is so small and so light compared to Earth’s core. The moon doesn't have much iron in it, scientists suggests that an object that size should have much more iron in it and hence big question is how do you make a whole object that has hardly any iron. The giant impact theory kind of answers this question as if it is piece out of Earth where Earth has already sunk its heavy elements like iron to its core and so mars-sized impactor that sideswipes the earth scattering Earth's crust into a ring around the Earth out of which moon is coalesced into the Moon. The Moon made of things that are very similar to the rocks and minerals we find on Earth like plagioclase feldspar, olivine and pyroxene, the things that make up most of the rocks of Earth's crust. The giant impact theory could explains many of such questions, but to convince people that something collided with the Earth 4 and a half billion years ago and created a lunar ocean magma scientists needed a little more evidence. An analysis of the moon rocks provided evidence that they are the same age as the oldest rocks found on earth supporting the idea that the Earth-Moon combination was the result of a massive collision.

 

 

Anorthosite can form by floatation of low-density plagioclase in the magma due to the density difference between plagioclase and melt. The extensive occurrence of anorthosite on the Moon requires a global magma body, referred to as the lunar magma ocean. So the highly anorthositic composition of the lunar crust, as well as the existence of KREEP-rich samples, suggest that a large portion of the Moon once was molten; and a giant impact scenario could easily have supplied the energy needed to form such a magma ocean thousands of kilometers deep. Also as from scientific study based on oxygen isotope ratios showed that the rocks on the moon and the rocks on the earth formed in the same place supporting the giant impact idea that the Theia collision hit was a sufficient force to homogenize the two planets mantles. The giant impact would have released enough energy to liquefy both the ejecta and the Earth's crust, forming a magma ocean. The liquefied ejecta could have then re-accreted into the Earth–Moon system. Similarly, the newly formed Moon would have had its own lunar magma ocean; its depth is estimated from about 500 km (300 miles) to 1,737 km (1,079 miles). So now you've got this giant of magma, lava and as it cools, things start to crystallize and the heavy minerals would sink out and the light minerals would float. And it turns out this white mineral plagioclase is less dense and it floated to the surface. So just like icebergs floats in an water ocean, anorthosite floats in magma ocean and eventually the entire surface covered with this anorthosite. And then you have billions of years of impacts and things get smashed and moved around. Anorthosites like the Genesis Rock turn out to be the oldest rocks on the moon, Apollo 16 later collected anorthosite samples that are both larger and older than Genesis Rock. Although 50 years later, today scientists are still learning from a collection of rocks, core samples, pebbles and dust that brought back from the Moon. And so thanks to NASA for putting a few humans on the moon to collect moon rocks, scientists were finally able to write the story of how the moon was created.

 

 

On Earth, impact craters are harder to recognize because of weathering and erosion of its surface. Also we have an atmosphere that slows down space intruders and turns them into shooting stars or meteors; most of them if small enough will be completely burned during this process. Although a small number of them will survive and make a hard landing and become meteorites. On the other hand, why does the Moon have so many craters while Earth has so few? The Moon lacks water, an atmosphere, and tectonic activity, three forces that erode Earth's surface and erase all but the most recent impacts. As there is no atmosphere on the moon, there is nothing to slow down asteroids and comets. There were lots of violent collisions from these impacting objects especially in the early time of our solar system. So these large objects went straight towards the moon's surface without slowing down and the collision fractured the crust and the mantle materials underneath found its way to the surface filling the basins at these crashing sites. Other than these larger impact events there are countless smaller objects gliding onto the lunar surface as well even to this day and this process repeatedly broke down the very top layer of the crust forming a dusty world that we see today. After billions of years of impacts with space rocks the outer 5 to 15 meters of the moon’s surface had been ground up into fine-grained stuff. We call this loose granular material as regolith. You might refer to it as lunar dust but it's very different from dust here on earth because there's no water flowing, no atmospheric water around the moon and it does not have any known form of plate tectonics. The lunar regolith is very important because it also stores information about the history of the Sun. The lunar soil is built up by repetitive bombardments and each impact throws out a little layer of ejecta, and so every time it does that exposes a new surface to the sun.  So these layers build one upon another through time and of course cosmic rays, solar wind are changes in the magnetic field affect the soils on the moon. The atoms that compose the solar wind – mostly helium, neon, carbon and nitrogen – hit the lunar surface and insert themselves into the mineral grains, a little sponge it soaks up all sorts of goodies from the solar wind. Upon analyzing the composition of the regolith, particularly its isotopic composition, it is possible to determine if the activity of the Sun has changed with time. We can predict the age of planetary surface with crater counting relative to other rocks on the moon. On earth, a billion-year-old rock is a very old rock whereas on the moon that would be one of the youngest rocks; as geologically earth is very dynamic and very young environment whereas the moon has been very static. It's sometimes difficult to maintain this dual perspective and although the Moon has billions years of static history, it’s still extremely important.

 

 

The main reason the Moon is important in the general understanding of the solar system is that it has no atmosphere, it never had any water erosions, it has no dynamic plates being formed as the Earth does and so the ages of Earth rocks have actually changed because of plate tectonics and erosion weathering process all kind of processes. It's quite amazing that how much the moon can teach us about our own planet as none of the things that have erased the earliest history of rocks on the Earth; like the motion of continents, the action of water and wind those things haven’t happened on the moon. Establishing the age of the Moon is critical to understanding Solar System evolution and the formation of rocky planets, including Earth. The oldest rocks on earth came in three categories. First, the rocks that formed here when the magma from the great impact solidified. Second, the rocks we brought back to earth from the moon and third, the rocks that landed on earth as meteorites. But most rocks on Earth are much younger than four billion years because of the constant recycling of the crust by plate tectonics—a process that does not occur on the moon. The moon rocks are older than 99.9% of rocks on earth and there may be older rocks buried deeper but we don't have access to them. The Moon rocks tells us what the early solar system was like up to about three and a half billion years ago and that's information we can't really get from any other accessible Planet. Thus, lunar samples provide an important glimpse of ancient rocks from the early days of the solar system. As there is no water, wind or atmosphere that interacts with the lunar surface, it has been preserved since its formation. If you look the Apollo 17 site with the Lunar Reconnaissance Orbiter and its wonderful camera from its orbit around the Moon, the Apollo astronauts' footsteps remain on the surface can be seen with the Lunar Reconnaissance Orbiter. One of the most important things we can do is to work in detail with the lunar regolith; the regolith is the debris layer that covers just about everything on the moon. It is developed over billions of years through impact processes as well as collecting information about the history of the sun. The solar wind is impacting the moon continuously that regolith records that energy as well as composition of the solar wind and lunar soils has the potential to implant of solar wind particles in it. We are beginning to see that potential, the lunar regolith is very important because it also stores information about the history of the Sun. So everything that had happened over 4.5 billion years ago is recorded in that lunar soil as being an archive that contains all the knowledge of the solar system climate like how the sun output might have changed over time. The moon is kind of like the rare book room of the cosmic library. So you go to the moon and can start paging through the earliest history of the solar system that beautifully preserved.

 

 

In 1609 Florence, Italy, Galileo Galilei had taken a newly invented telescope and aimed it at the moon. He used an early telescope to make drawings of the Moon for his book Sidereus Nuncius, and deduced that it was not smooth but had mountains and craters. Sketches of the moon from Galileo’s “Sidereus Nuncius,” a short treatise on Galileo’s early observations of the Moon, the stars, and the moons of Jupiter; it was the first scientific treatise based on observations made through a telescope. Look at his sketches created over years ago! These observations proved that the surface of the Moon is not smooth as previously thought but rather uneven and full of cavities. The conclusion he drew was that the changing dark lines were shadows and that the lunar surface has mountains and valleys. In his sketches, we can see clearly that the line between the light and dark sides of the Moon that looks so straight with the unaided eye, is in fact ragged from the long shadows cast by mountain ranges and (as we know now) craters. Before Galileo’s observations the Moon was thought to be a perfect, smooth sphere. Galileo described the surface of the moon as being uneven and rough and crowded with depressions and bulges. The Moon was thus not spherical and hardly perfect. In fact, the surface of the Moon was pretty much like the surface of the Earth! So like on Earth, the darker, low-lying areas were seas, so he called them “Maria” (Latin for Sea). Apollo 11 touched down in one of these, the “Sea of Tranquility”. The moon’s highlands, on the other hand, were lighter in color, like the spot where Apollo 16 landed. And many of the shadowy shapes Galileo saw we later realized were impact craters. By his own account, Galileo first observed the Moon on November 30, 1609 and now four centuries later on November 30, 2022, with Artemis I mission Orion Spacecraft was orbiting around the moon and sending photographs. Throughout history, we have chased the horizon to seek what lies beyond. We have an inbred thing in us that inspires us to explore and seek knowledge in the process that's what we do on this planet. The hope of the next generation of scientists is that by studying new samples of rock they can unlock many more of the Moon’s secrets and even some of the Earth’s.

 

 

The Artemis 1 splashdown occurred exactly 50 years to the day of NASA's Apollo 17 moon landing. Fifty years ago, Astronauts Gene Cernan, Harrison Schmitt successfully landed on the Moon, while Ronald Evans orbited in the CSM. That was the last successful mission of Apollo program. Fifty years later, it was the first successful mission of Artemis program. The “Blue Marble” is an image of Earth taken on December 7, 1972, from a distance of around 29,000 kilometers (18,000 miles) from the planet's surface. It was photographed by NASA Apollo Astronaut Harrison Schmitt on Apollo 17 spacecraft as it travelled towards the Moon. Blue Marble is one of the most famous; most viewed and most reproduced images in history. From deep in space, our Earth appeared to the astronauts as a small blue marble and hence the name. About over 71 percent of the Earth's surface is water-covered, hence from outer space it appears blue with some parts are brown, yellow, green and white swirls. After 50 years, Artemis 1 mission has captured imagery of Earth and itself while in transit to the Moon. Orion spacecraft was at a distance of around 92,000 kilometers (57,000 miles) from the Earth. The most recent boot-print on the moon was left December 14, 1972, no human has stepped foot on the moon since then. Cernan and Schmitt successfully lifted off from the lunar surface in the ascent stage of the LM on December 14, at 5:54 p.m. EST. The return to lunar orbit took just over seven minutes. The LM, piloted by Cernan, and the CSM, piloted by Evans, maneuvered, and re-docked about two hours after liftoff from the surface. Once the docking had taken place, the crew transferred equipment and lunar samples from the LM to the CSM for return to Earth. “We leave as we came,” NASA Astronaut Eugene Cernan said, “and, God willing, as we shall return, with peace and hope for all mankind." Those were the last words spoken on the moon by astronaut Gene Cernan, during the Apollo 17 mission, on December 14, 1972. Apollo 17 was the sixth and final mission of the Apollo program and most notably the last time humans set foot on the moon's surface. The Apollo program, which landed the first human on the Moon, ended in December 1972 with Apollo 17. But as after fifty years of Apollo program and first successful Artemis mission in December 2022, we are getting ready to embark that journey again. We continue to build on the legacy of the Apollo program as the Artemis Generation prepares to go farther into the cosmos than ever before. The 50th anniversary of Apollo 17 reminded us that this mission was a crucial stepping stone in the history of lunar science laying the groundwork for its future missions like LRO which in turn helping scientists in opening the door on a new era of human exploration with Artemis. So these missions may be separated by Decades of time they all interconnect with the central premise and understanding of how the Moon is the Cornerstone to understanding our universe. The Apollo 17 anniversary allowed us to reflect on all the moments big and small that led to the success of that historic mission.

 

 

The importance of the Apollo 17 mission as the final exploration mission of the Apollo series was that it could go to a very complex area with a geologist on board that could resolve some of these questions or at least collect samples that could not be collected maybe anywhere else with the Apollo capabilities. So that through the next many decades of analysis would begin to answer some of the unresolved questions about the history of the moon, turns out that through the discovery of the orange soil that Schmitt made at a crater called shorty that though appearing as a young material, was actually a very old that about 3.5 billion years old when it erupted. During an EVA, Apollo 17 Astronauts were communicating constantly with Mission Control. Schmitt was digging trenches, observing and learning while sampling the lunar material. The discovery of orange soil caused great excitement among the scientists at Mission Control, who felt that the astronauts may have discovered a volcanic vent. However, post-mission sample analysis revealed that Shorty is not a volcanic vent, but rather an impact crater. In the early days of the Apollo Program, the Board leaned toward the moon landing sites that were safe and easily accessible, if not the most scientifically interesting. The safe and accessible regions with good illumination from the Sun during the entire mission and across which 5 to 8 km smooth around without any dangerous mountains or craters, or steep slopes. That’s why smooth mare areas were chosen for the first three Apollo landings. However, the last three Apollo Moon landings were entirely focused on serious scientific exploration of the Moon. That led to the selection of landing sites that were scientifically intriguing, even if the operational aspects — rugged terrain, landing approach paths through mountain passes, etc. — were much more challenging. Apollo 15 was the first of three “J missions” that carried lunar roving vehicle and designed for longer stays on the Moon, often called the true scientific missions to the moon. But as Apollo 17 approached our understanding of the Moon’s history remained incomplete. The Moon rocks and soil collected so far were dominated by materials from lowland lunar maria (Latin for “seas”). However, the Moon is mostly composed of highland material, which accounts for nearly 85 percent of the lunar surface. Scientists knew a complete picture of lunar evolution couldn’t possibly be developed without highland samples. Since Apollo 17 was to be the final lunar landing of the Apollo program, high-priority landing sites that had not been visited previously were given consideration for potential exploration as it would be the last chance for astronauts to gather such material. So, NASA decided Apollo 17 should land at a highland site. The only question was where? A significant reason for the selection of Taurus–Littrow was that Apollo 15's Command Module (CM) Pilot Al Worden had overflown the site and observed features he described as likely volcanic in nature. And so the Serenitatis site was classified as a volcanic site based on photographs taken by Apollo 15 which seemed to indicate the presence of volcanic craters. At Taurus–Littrow, it was believed that the crew would be able to obtain samples of old highland material from the remnants of a landslide event that occurred on the south wall of the valley and the possibility of relatively young, explosive volcanic activity in the area. For mission planners, Taurus-Littrow valley was a crossroads of lunar history: The floor was covered in dark volcanic rocks, but boulders and lighter material that had fallen from the surrounding mountains offered access to ancient highland material. So this intriguing site offered astronauts an opportunity to gather older highland sample as well as younger volcanic samples, a prospect which generated much excitement among the lunar science community.

 

 

The valley of Taurus-Littrow was the Apollo program’s most ambitious landing site. It runs roughly east-west between two massifs to the north and south that are taller than the Grand Canyon is deep. A third massif and a slighter range called the Sculptured Hills sit at the eastern end of the valley; the western end opens into Mare Serenitatis. In the Lunar Module (LM) Challenger, Cernan and Schmitt approached from the east, soaring over the hills and descending between the North and South massifs. In contrast to Earth, no major lunar mountains are believed to have formed as a result of tectonic events. Mountains on the Moon are mostly parts of the upthrust rims of ancient impact basins. The landing site was Taurus-Littrow, a valley on the southeastern rim of Mare Serenitatis (Sea of Serenity). The mountains on either side of the valley rise to thousands of feet in elevation that Schmitt called a “geologist’s paradise” as you can see three dimensions of at least the upper crust of the moon. Taurus-Littrow is not only a beautiful location; it also contains a unique mix of lunar geological features. This charming little valley where the Apollo 17 landed is nestled between two soaring mountain ridges named North Massif and South Massif. These Massifs are so tall that the valley floor between them is deeper than the Grand Canyon! So its huge massifs that believed to be formed by the impact that created the Serenitatis basin. And together, they create a classic graben, a geological feature that occurs on Earth when two parallel mountains rise up, forming a deep valley between them. A lunar graben has different origins than an Earth graben as the lunar mountains formed as a result of a giant impact, but the result was the same: a small, square valley tucked between the massifs. A lunar graben has different origins than an Earth graben as the lunar mountains formed as a result of a giant impact, but the result was the same: a small, square valley tucked between the massifs. It was hemmed in by mountains as high as 7,900 feet (2,400 m), which were heaved upward in the massive impact that formed the Serenitatis basin. Since then, volcanoes and impacts had further sculpted the area. Features included landslides, ejected boulders that had scraped tracks into the lunar soil, and a 260-foot-tall (80 m) scarp — the remains of a fault line — that cut across the 4.4 mile-wide (7 kilometers) valley. All-in-all, the Taurus-Littrow valley offered the very real possibility of collecting both very young and very old lunar material.

 

 

Apollo 17 astronauts collected samples from the valley of Taurus-Littrow in December 1972. They had the lunar roving vehicle and so they covered the longest distances of any of the missions looking to things like impact craters or landslides that deliver material from farther away which you might not be able to get. Astronauts have to make the judgment calls about what you see around you and try to collect some sample of multiple different things that are going on, as part of that history that story that you're seeing in the rocks. One technique Apollo 17 astronauts used was to look up hills and see if any boulders had rolled down the hill, they did that in their mission they identified some places where rocks from a good distance away had come to them so they were able to sample them. Another reason why they particularly sampled this region with the core sample was that site has the landslide deposit very close to a fault which is basically a gigantic crack. Scientists said one of the goals to sample deep within that surface was to capture any potential gases as the hope was that the fault line would be a conduit to the gases that are from within the moon that slowly de-gas outside of the moon and delivered into this landslide deposit which then can be captured by double drive tube. And that was one of the reasons why tube was sealed in a vacuum container to really capture those gases. NASA curators works to preserve the lunar samples for ongoing and future scientific research, the samples are protected in secure and environmentally controlled vaults. Sample 73001 was first vacuum sealed on the Moon and then stored in a second protective outer vacuum tube inside the nitrogen-purged core sample vacuum container (CSVC). Scientists from around the world study and analyze the samples to answer important questions about the moon's formation and history, to preserve the integrity of these samples NASA curators follow strict safety and handling processes when working with samples. Fifty Years Later, NASA Curators unveiled one of last sealed Apollo tube samples. The Lunar core sample ANGSA 73001 has remained sealed since lunar acquisition, but it has finally been opened and being studied. Native stratigraphy of the collected material remains preserved in the tubes, analyses to date show that regolith within the deeper section of the Apollo 17 73001/2 "landslide" core. The Apollo 17 core sample dubbed 73001 came from the foot of the South Massif. It is the bottom segment of a double drive tube, from below 22 cm depth that was retrieved from the surface by the Apollo 17 mission astronauts Gene Cernan and Jack Schmitt.

 

 

One of the techniques used by Apollo astronauts for sampling the surface of the Moon is the use of some short core tubes. These tubes get down to a depth of 70 centimeters and so very important means to get a very well preserved sample. Apollo astronauts learned during Apollo 15 mission that down to the depth 70 centimeters you have a minimum temperature zone that's very stable as the ground above it is highly insulating, so at that depth temperature is about minus 20 degrees centigrade which means it's a cold trap. So the volatile elements that are moving around within the soil will tend to concentrate there. Hence it is probably one of the most valuable samples as we can start to learn about these trace elements, about the lunar atmosphere and about what kind of gases does a planet evolve. The moon is not big enough to hold the gases but it is almost certainly evolving gases and we need to know more about that if we're going to understand the origins of our own hydrosphere and atmosphere on the Earth. In year 2019, with the Apollo next generation sample analysis initiative (ANGSA), NASA scientists opened core tube from Apollo 17 mission and as it's very cold there on the Moon any potential gases and volatiles that were trapped down there get sealed and preserved into this vacuum container. Today’s technologists developed a gas extraction technology for this particular purpose as it is important to study these gases from the deep within lunar surface, so the gas then stored in the canisters and distributed to different scientists. Fifty years ago, we went with Apollo program and now we're going again with Artemis program but we're going to a very different place, we're going to the south pole of the moon. And in the South Pole there are some locations that are permanently shadowed because the sun is coming at a very oblique angle to the very bottom of the Moon; there are some depressions impact craters created by debris from space that has hit the moon in the past and made a depression. These depressions never see sunlight down there and so called permanently shadowed regions (PSR). Scientists believe these PSRs may contain water that maybe was delivered to the moon by comets or potentially from within the moon itself that gets into one of these traps and stuck there. Scientists call these as cold traps and so some of the samples that they hope to collect now in the upcoming missions of the Artemis program. So it turns out our next mission to the lunar surface involves a lot of rock and soil collection. So if all things going well, we will go back up to the moon again with Artemis mission and still there going to be more moon rocks collection. Scientists are hoping that if core tube collected during Artemis mission from the cold traps at permanently shadowed regions might contain volatiles with them and so technologies developed for Apollo moon sample study will be at the ready for Artemis moon sample, so it will be little bit easier if you have the right tools. And also to make sure that we get the best samples from the south pole of the moon so that scientists can study it. So we can understand the water cycle and whether or not the water could be used as a resource for Artemis astronauts.

 

 

The Apollo 17 landing site in the Taurus-Littrow Valley was selected such that astronauts could collect samples of the lunar Highlands and investigate the volcanic history of the area. In 2022, scientists from the Apollo Next Generation Sample Analysis Program, or ANGSA group looked at a double drive tube of material collected on Apollo 17 by astronaut Gene Cernan that he hammered into the Moon’s ground until the hollow part of the tube filled with rocks and soil. The one side of the core is the lunar surface and the other side of the core represents 22 centimeters of depth going into the lunar ground, so that's what the lunar surface looks 22 centimeters underneath it. The sample was split up so that it could be studied in a bunch of different ways, ANGSA scientists dissected the core meaning that taking apart bits by bits to see different colors, to find little pieces of rocks and discover potential layers. Every half centimeter of this sample and then stored in little containers to preserve any potential layers that we can't really see with our eyes. The one side of the core you can see that the beginning of the core is a lot darker, so the Moon's surface is a little bit darker than the rocks in soil underneath the surface. So all of this will give us information about the area where the sample comes from and how the moon formed and evolved over time. So far, we know that the material in  this tube starts looking a lot different once you get past the surface, going from  less soil to more rock and mineral-like. This means that the Moon’s surface here was layered, possibly because of some sort of landslide after an asteroid hit the surface. Based on the analysis of photographic images that had been taken prior to the Apollo 17 mission, Apollo era scientists knew that the distinct high reflectance deposit that spreads across the Taurus Littrow valley floor formed as a giant landslide from the north face of South Massif. There was clear evidence of a landslide on the South Massif, where lighter material had spilled off the mountain and into the darker valley floor below, allowing for easy sampling. The primary goal was to resolve through observation and sampling some of the unresolved questions about the history of the moon. For any geologic problem to tackle needs sample from several different locations, so that we can understand processes that may be in effect across broader regions, so as a landslide as noted here. Sampling the landslide was an objective of the Apollo 17 mission. Apollo era scientists proposed that the landslide was caused by ejecta from Tycho crater landing on the summit and south side of the massif. The resulting seismic jolt sent regolith sliding down the steep North Slope resulting in the distinctive landslide we see today. The scientists would want to collect from inside the landslide, adjacent to the landslide. By determining how long rocks had sat on the surface of the slide scientists could know the timing of the formation of Tycho crater, which is more than 2000 kilometers to the southwest. Apollo era scientists looked closely at the summit which appears to be dark and blocky material, so they thought it may be deposits of solidified impact melt from the Tycho event. As it turns out, the exposure ages of the samples brought back from the landslide were about 110 million years - thus Tycho crater was assigned that age.

 

 

Over three decades after Apollo 17, NASA launched the Lunar Reconnaissance Orbiter (LRO) in 2009. So LRO has now been on treasure hunt for over 14 years and has provided a treasure trove of new information about the Moon. The scientific instruments aboard this robotic spacecraft collect a wide variety of scientific data on the Moon's environment including surface and subsurface properties. It has the capacity to help scientists reinterpret older data and answer scientific questions that had been lingering from the days of Apollo 17. One such case involved the debate over the origins of a light-colored mantle seen at the base of the South Massif in the Taurus-Littrow Valley; LRO imagery provided a key discovery that enabled scientists to put together the many pieces of the puzzle. Map view of North Slope of South Massif, edge of summit seen in lower left; a two lobe landslide spreads across the relatively flat floor of the valley, partially covering the mighty Lee Lincoln scarp. LRO photographs made it very clear that there was an older slightly darker avalanche underlying partially underlying the light colored light mantle. Avalanche immediately brought into question whether or not the light mantle avalanche that people had thought it was triggered by secondary material thrown from a the crater Tycho some 2000 kilometers to the Southwest. It would seem it's not impossible but it would seem to be very coincidental to have two Avalanches, one of which was triggered by those impacts and that in turn took us to looking at what might be an alternative triggering mechanism. As the scientists begin to understand the Lee-Lincoln scarp with LRO’s new mapping and analysis of the area that brought forward the alternative idea which is that the landslide was caused by motion along the Lee Lincoln fault. It is certainly logical that seismic shaking along such a massive fault could cause a landslide. A second hypothesis reported at the 49th Lunar and Planetary Science Conference in year 2018 that it was indeed a thrust fault scarp that scientists thinks maybe are being triggered by seismic activity that is to say moonquakes. The paper (authored by Apollo 17 astronaut Harrison Schmitt) proposes that there were actually two large quakes and thus two landslides, the younger covering most of the older. The older deposit (smaller lobe on the right) is distinguished by its lower reflectance relative to the brighter younger slide (left side). Apollo 17 Commander Eugene Cernan and Lunar Module Pilot Jack Schmitt drove their Lunar Roving Vehicle across Lee-Lincoln scarp ridge during their second EVA on the Moon. The Lee Lincoln scarp is a low ridge or step about 80 meters high and running north-south through the western end of the Taurus-Littrow valley. These ridges are common on the Moon as thousands of lobate scarps scattered over lunar surface from pole to pole, with more discovered all the time. During the Apollo program astronauts have visited just one lobate scarp; the Lee Lincoln scarp is the only extraterrestrial fault scarp to be explored by humans (astronauts Eugene Cernan and Harrison Schmitt). The Lee-Lincoln scarp is an example of an important class of lunar tectonic features called lobate scarps. This lobate scarp marks the location of a relatively young, low-angle thrust fault. Lobate scarps are long, curvilinear structures found on some planetary bodies. They are interpreted to be tectonic in nature, the result of a thrust fault developed in rocks that are otherwise structurally sound. So if Dr. Schmitt is correct then we do not know the age of Tycho crater which in turn has implications for how scientists estimate the ages of other young craters across the Moon and other inner Solar System bodies as the their ages are being derived from Crater Counting approach for which the calibration provided by the Lunar samples brought back during the six Apollo missions between 1969 and 1972.

 

 

We celebrated the 50th anniversary of NASA's Apollo program. The years 2019 to 2022 marked the 50th anniversary of the Apollo Program that landed a dozen Americans on the Moon between July 1969 and December 1972. The Apollo lunar flights may have ended in 1972, but the lunar samples brought by the Apollo missions are still teaching today's scientist stunning new things. One of the reasons why NASA kept these samples safe for 50 years was that they knew that technology will evolve with time. The x-ray computed tomography (XCT scanning) that from medicine when doctors scan for displaying a cross section through a human body without actually cutting it open. That's the technology that didn't really exist to that extent 50 years ago which gives us the chance to take rocks you know like big rocks or drive tubes.  So now we can look inside the sample and we can see the minerals and we can see the texture and learn a lot about where the sample comes from within the moon, and how it formed without actually contaminating it or breaking it. The mass spectrometers have evolved over time too, so now less samples are needed to get higher precision higher quality data and so again that wasn't possible 50 years ago. It's been 50 years since humans last stepped foot on the moon, Apollo 17 sent the first and only geologist to the moon. While explaining how Apollo 17 mission does connects with NASA's current exploration of the Moon and our future plans to return humans to the surface, geologist and lunar module pilot for Apollo 17 Harrison Schmitt said, “The quality and diversity of the Apollo sample collection is absolutely remarkable and it's a gift that keeps on giving the researchers continue to go back to these samples and as new analytical technology comes along where you can apply new techniques get more higher resolution information and that will be going on indefinitely, I don't think the lunar sample collection from Apollo will ever be out of date.” He also mentioned that one of the most important tools that they had was “double drive tube” that you could drive into the moon surface and as they got us quite a number of very good cores that are giving us new information. It was anticipated early on in the Apollo program that analytical technology would mature would become much more sophisticated with time that we could gain new information from the same old samples which makes it very exciting for everybody, so it seems like Apollo never ended for lunar scientists. The ANGSA team got to open one of the very special samples that never opened before as they were ready to study untouched Moon rocks for the first time in over fifty years using 21st century technology. Although today our technology is better than as it was in the 1970’s, it will probably be even better in the 2040’s. There are still pristine moon samples unsealed unstudied until now saved for the next generation of researchers with future’s further developed technologies. When geologists look at lunar samples, the sense of awe and wonder doesn't get old. In fact that makes them childlike curious. So it's a very humbling experience for them to study those samples which Apollo astronauts brought back to Earth from another celestial body.

 

 

Cernan and Schmitt completed three moonwalks in the Taurus–Littrow valley, took lunar samples and deployed scientific instruments. They discovered orange soil at Shorty crater containing very small beads of volcanic glass formed over 3.5 billion years ago. Its scientific analysis showed that it is volcanic in origin and a remnant of a fire fountain that sprayed molten lava high into the lunar sky in the Moon's early days long before Shorty's creation. So these orange volcanic beads were droplets of molten lava from the fountain that solidified and were buried by lava deposits until exposed by the impact that formed Shorty, less than 20 million years ago. It took 36 years analyzing those samples to figure out there was water and other volatiles in the moon as when scientists looked at the orange soil, they found volcanic glass beads, glass-like volcanic rock formed by the rapid solidification of lava without crystallization. When you look at those lunar soils, one of the most dramatic things about these tiny gorgeous glassy spheres from orange soil found while Schmitt was examining the edge of the Shorty crater turned out to be volcanic ash like the colorful rocks around the volcano in New Mexico. They are volcanic spheres that were exploded out of the surface, so for the first time we learned about lunar volcanism that must have been explosive because they're spheres it means there must have been some kind of explosion and some kind of fluid vapor water probably that caused that explosion. These beads were formed back when the Moon was still volcanically active. Fire fountains launch droplets of lava into space, where they cooled rapidly and then fell back to the surface. This gave us a hint that we had these fire fountain kinds of events going on as we see in Hawaii, the first hint of volatiles but we couldn't measure them as we didn't have the technology to measure volatiles in these very tiny orange glass beads. As initially the Moon seemed bone dry and certainly we don't see the water on the Moon and minerals that contain lots of water as you do on Earth. The very first experiments people did to answer this were to take those tiny spheres and measure the water content and it turns out there's just not that much water in the spheres on average. In 2007 these beads or tiny glass-like spheres were sliced to a fraction of a millimeter across and tested for water with a very sensitive instrument called a nanoprobe. After analyzing the entire sphere the total amount of water measured as hydrogen was just simply not very large but when scientists looked more closely they surprised with the hydrogen content across the sphere, very low at the edges of the sphere but as you go towards the middle there was this huge peak, much more water in the center of the sphere. The results showed significant amount of water with concentrations highest in the middle of the beads. It reveals there's hundreds of parts per million water in those lunar volcanic rocks and that's enough water to drive explosive volcanism. This indicates that the water must have been trapped there during the initial eruption, it's enough water to tell us that there's a lot more water on the moon than we originally suspected. For a long time we used to think the Moon was completely dry but now we know that hypothesis is all wet and the picture is definitely muddier than it used to be, that naturally makes scientists wonder whether the original samples were just super-dry or the instruments in the seventies weren’t sensitive enough to see the water in them. We simply didn't have the technology to be able to detect it, as it wasn't until 2008 that we found that the volatiles were present and once we did it opened up a whole realm of possibilities. Volcanic lava beads that brought back to Earth aboard Apollo 15, showed small amounts of water in their interior. In May 2011, 615–1410 ppm water in melt inclusions in lunar sample 74220 was reported, the famous high-titanium "orange glass soil" of volcanic origin collected during the Apollo 17 mission in 1972. The inclusions were formed during explosive eruptions on the Moon approximately 3.7 billion years ago. This concentration is comparable with that of magma in Earth's upper mantle. Although of considerable selenological interest, this insight does not mean that water is easily available since the sample originated many kilometers below the surface, and the inclusions (particles of distinct composition embedded in rocks) are so difficult to access that it took 39 years to find them with a state-of-the-art ion microprobe instrument.

 

 

Liquid water cannot persist on the lunar surface as it is exposed to charged particles from the solar wind as well as galactic cosmic radiation. When exposed to solar radiation, water quickly decomposes through a process known as photo dissociation and is lost to space. However, there are a few regions of the Moon which might have protected water for billions of years that never see sunlight. These areas are called permanently shadowed regions, and they appear dark because unlike on the Earth, the axis of the Moon is nearly perpendicular to the direction of the Sun's light. The Moon’s South Pole, sunlight strikes at a low angle, so if you were standing on the Moon’s South Pole, you’d see the Sun down on the horizon, casting long shadows across the lunar surface. The bottoms of certain craters, like at the Moon's South Pole which are never pointed toward the Sun, with some remaining dark for over two billion years. However, thanks to new data from NASA's Lunar Reconnaissance Orbiter (LRO), we can now see into these dark craters in incredible detail. Seeing the shape of the crater is important, and LRO has used its LOLA instrument to make the best yet topographical maps of these craters by reflecting lasers off the lunar surface. This has allowed us to see the shapes of the craters' interiors from any angle, and by making 3D models, we can light up the crater floors as if we had a giant flashlight. Now with Artemis program we are going to the South Polar Region which is more representative compared to Apollo as we don't really expect a lot of basalts there, so that's more like a Highland region. The topography of the Moon has been measured with laser altimetry and stereo image analysis. The South Polar Region also has the largest impact Basin that we have on the moon and also the oldest, as the South Pole–Aitken basin approximately 2,400 km in diameter, the largest crater on the Moon and the second-largest confirmed impact crater in the Solar System. At 13 km (8.1 mi) deep, its floor is the lowest point on the surface of the Moon. So if we can bring back rocks from there we can hopefully date really old impact region and then get a better idea of when things happened on the moon and establish a timeline. We also know that the Polar Regions are really cold, so any volatiles and gases on the Moon might freeze out in that region. So collecting the rocks there and bring back these frozen samples can teach us something about where the water is coming from, whether its moon or the asteroids and comets that impacted the Moon. So we can also learn about something about the water that was delivered to the Earth Moon system which most likely also ended up on Earth. So we can learn not only how the moon formed and evolved over time but something about our own history.

 

 

Since the 1960s, scientists have hypothesized that water ice may be deposited by impacting comets or possibly produced by the reaction of oxygen-rich lunar rocks, and hydrogen from solar wind, leaving traces of water which could possibly persist in cold, permanently shadowed craters at either pole on the Moon. Because of the lack of atmosphere, temperatures of different areas vary particularly upon whether they are in sunlight or shadows, making topographical details play a decisive role on local surface temperatures. Parts of many craters, particularly the bottoms of many polar craters sunlight never reaches, are permanently shadowed; these "craters of eternal darkness" have extremely low temperatures. These craters are some of the coldest places in the whole solar system, colder than the surface of Pluto. The Lunar Reconnaissance Orbiter measured the lowest summer temperatures in craters at the southern pole at 35 K (−238 °C; −397 °F), regions where there could be permanent ice deposits that have been there for billions of years. As you watch the Moon over the course of a month, you'll notice that different features are illuminated by the Sun at different times. Almost every part of the Moon is constantly bathed in sunlight, or cloaked in darkness. During the lunar day, temperatures reach 120-degrees C (or 253 Fahrenheit), and then during the lunar night, temperatures drop down to -232 C (or -387 Fahrenheit). In other words, during the daytime, it’s definitely hot enough to sublimate away that ice. It took 36 years from when we last left the moon to discover there was water on the Moon. In 2008, using NASA made Moon Mineralogy Mapper (M3) on board the Chandrayaan-1 spacecraft scientists confirmed the existence of surface water ice. They detected water vapor which found to vary with latitude and possibly generated from the sublimation of water ice in the regolith. Since the permanently shadowed regions maintain such a consistently low temperature, they act as cold traps places where volatiles like water remained frozen as ice. The ice deposits were found on the North and South poles, although it is more abundant in the South, where water is trapped in permanently shadowed craters and crevices, allowing it to persist as ice on the surface since they are shielded from the sun. These are areas of the Moon which seem to have a lot of water mixed in with the regolith. Once thought to be bone-dry, right now we have a tantalizing hint that there are vast stores of water ice at the Moon’s South Pole, that’s accessible to human and robotic explorers as scientists have found that the Moon has vast deposits of water ice, especially at the South Pole, near which Artemis III mission is set to land.

 

 

NASA in collaboration with its partners is preparing to return to the Moon by 2024 as part of its Artemis program, the agency is focusing its efforts on exploring the Moon’s Polar Regions. There, water ice has accumulated for billions of years from a variety of sources, kept stable in permanently shadowed regions (PSRs). Yet on the rim of some craters in the polar region, the sun shines nearly constantly. It’s the perfect combination of power for solar panels and water for drinking, making oxygen and making rocket fuel. This is a critical resource, and the Moon might be just the place to help humanity as it pushes out to explore the rest of the Solar System. Over the next decade, the Moon is going to get much busier, it’s partly because between China’s robotic missions and NASA’s Artemis program. Other agencies are planning a series of missions and experiments, there are multiple missions planned by Russia, India and Japan, and a bunch of private landers. There’s a lot of interest in the Moon lately as knowing whether there’s water on the Moon that would help us know to sustain a colony up there someday. Because water isn’t just water, but it’s also hydrogen and oxygen that means is breathable air and rocket fuel. Over the next few years, robots and then people will study this region very carefully, building up the evidence. If we’re lucky, the Moon will have everything we need to take a big step off Earth, and out into the Solar System. Hence one of the Artemis goals is to deliver robotics, science instruments to the surface and paving the way for human missions in 2024. With Artemis missions, NASA in collaboration with commercial and international partners will establish the first long-term presence on the Moon. The objective is to utilize innovative technologies so that Artemis moonwalkers can explore more of the lunar surface than ever before. In 2024, NASA will send a rover called VIPER (Volatiles Investigating Polar Exploration Rover) to that region to scout out what will surely be a dramatic landscape.

 

 

In contrast to Earth, no major lunar mountains are believed to have formed as a result of tectonic events. Mountains on the Moon are mostly parts of the upthrust rims of ancient impact basins. Scientists recently named a mesa-like lunar mountain that towers above the landscape carved by craters near the Moon's South Pole. Melba Mouton, an award-winning mathematician, computer programmer, and African American trailblazer is being honored with the naming of a mountain at the Moon's South Pole. She was a mathematician and computer programmer in NASA's Trajectory and Geodynamics Division in the 1960s. She served as the Assistant Chief of Research Programs and headed a group of NASA mathematicians called "computers". She was instrumental in coding computer programs that calculated spacecraft trajectories and locations. Before retiring, she was recognized with a NASA award for her calculations of complex mathematical data that contributed to the successful Apollo 11 Moon landing. To recognize her contributions to the agency, NASA proposed the name Mons Mouton for the lunar landing site and exploration area for VIPER, its first robotic Moon rover. NASA's Volatiles Investigating Polar Exploration Rover, or VIPER, is a mobile robot that will go to the South Pole of the Moon to get a close-up view of the location and concentration of water ice. Mons Mouton is a mountain that stretches roughly 2,700 square miles and has an elevation of more than 19,000 feet. VIPER will embark on a 100 day journey at Mons Mouton and as a robotic trailblazer; it will make a new track through the unexplored areas. The rover will be tasked with prospecting for lunar resources in permanently shadowed areas in the lunar South Pole region, especially by mapping the distribution and concentration of water ice, in places where we do not have good "scouting" images from orbit. VIPER will scout the lunar South Pole to search for ice and other potential resources to help enable long-term human exploration of the Moon. The history of the Moon isn’t wrapped up just yet. There is lot of science is awaiting as future planned Artemis crewed mission, Artemis II is now being conceived and hopefully we can land crew by Artemis III. Even without a crew, Artemis I was a record-breaker. Through Artemis missions, NASA will land the first woman and the first person of color on the Moon, paving the way for long-term lunar presence. The rover will explore the Moon's surface to help gain a better understanding of the origin of lunar water as well as map potential resources, which will help inform future landing sites under NASA's Artemis program. The objective is to utilize innovative technologies such as VIPER so that Artemis moonwalkers can explore more of the lunar surface than ever before. Melba worked at NASA's Goddard Space Flight Center, coding computer programs to calculate the trajectories and locations of various aircraft. Her legacy lives on at the highest peak in the lunar South Pole, bringing NASA a step closer to its goal for a long-term presence on the Moon.

 

 

Our understanding of the Moon today is vastly different from that during the age of Apollo. In 1968, when NASA announced the five landing sites for the Apollo missions; all of them were in roughly the same latitude across the lunar surface - a strip that extended just a couple of degrees above and below the Moon’s equator. The safe and accessible regions with good illumination from the Sun during the entire mission and across which 5 to 8 km smooth around without any dangerous mountains or craters, or steep slopes. All of the landing sites had to be within the region of a free-return trajectory back to Earth, and using the least amount of propellant possible; hence the Moon’s near side. Moon rocks on Earth come from four sources: those collected by six United States Apollo program crewed lunar landings from 1969 to 1972; those collected by three Soviet uncrewed Luna probes in the 1970s; those collected by the Chinese Lunar Exploration Program's uncrewed Chang'e-5 mission; and rocks that were ejected naturally from the lunar surface before falling to Earth as lunar meteorites. That's not a lot of area and people are still learning new things from these rocks. We have learned so much but we have just scraped the surface about the moon and how it can enable technology, how it can enable exploration and how it can enable science. So for science it preserves an awful lot of things that we've been completely obliterated on this planet it tells us an awful lot about what has gone on in the early solar system. Apollo samples are the gift that keeps on giving and that's awesome. But the samples given out now for research are very tiny, when they gets below 50% of the original mass of that sample it doesn't go out, so you can't get any more unless it is  really well justified. There are very strict rules about analyzing those samples, and you have to apply to a committee. Despite their old age, we’re still learning new things from the moon rocks. We still have some moon samples from Apollo that still haven't been opened, they were special samples taken under extreme cold, vacuum and in the shadow. There is still exciting stuff to be learned from such sample collection. But with Apollo we're missing a lot of rocks and processes with Apollo and hopefully we can fill these gaps with Artemis. And so Artemis program is important because having access to wide range of materials would be good to conduct the various kinds of experiments and to develop new technologies to study pristine Apollo samples. Unlike the Apollo mission when Artemis missions will go to the Moon, it’s going to be even more challenging, since they will be heading to the South Pole.

 

 

If you look the Moon with the Lunar Reconnaissance Orbiter and its wonderful camera from its orbit around the Moon, these wonderful new images we have with us as this mission that is still orbiting the moon today. It's been up there since 2009 and it has this high-resolution camera that have mapped now the entire moon and you've got the near side and the far side and you can see the dichotomy between the two surfaces. We have an immense crater on the far side of the moon it's 2500 kilometers across, it's the largest impact object anywhere in our solar system that we know about and so that excavated deep into the moon's surface probably below the crust, but then we have additional meteorites asteroids crashing down excavating even deeper and so much of the mantle of the moon has been thrown out onto the surface where we can study it directly. So this is a whole new thing the far side of the moon holds pieces of the moon's mantle that tells us something about the structure of the moon that we never knew before. There is huge opportunity on the far side to see geology that's different than on the near side. That gives us an opportunity but we've never been able to go there we're never able to land and it's only very recently in 2019 that a Chinese mission that's the Chang’e-4 mission landed on the far side. China landed the world’s 1st spacecraft on the far side of the Moon during Chang’e-4 mission in 2018 and the rover operates to this day! China’s Chang’e-4 Lander and Yutu-2 rover are at the Moon’s South Pole right now, crawling around, exploring the region, and sampling the lunar regolith. They landed in the Von Kármán crater in the South Pole–Aitken basin and have been there since January 3, 2019, and can only operate during the lunar day, when there’s sunlight to keep their instruments working. NASA’s Lunar Reconnaissance Orbiter has even photographed them as it orbits overhead. It turns out on the far side of the moon it's a different story with that huge impact and then additional craters landing inside the big crater you can actually excavate pieces of the moon's mantle. Chang’e-4 was able to analyze the soils and the rocks and found something really amazing that far side is made largely of pyroxene and olivine two minerals that we think are dominant in earth's mantle. So the Moon is formed much like the earth in layers, a differentiated body, with a crust, mantle, and core. The Moon is anomalous in having a core a relatively tiny core about 390 kilometers in diameter, very thick mantle and a fairly thin crust which we can tell from seismic measurements on the Moon by running seismic sound waves through the moon and seeing how that reflects. In next mission Chinese moon mission Chang'e-5, it revealed further the possibility that a unique aspect of the Moon’s mantle composition could have resulted in a lower melting temperature, therefore explaining how the molten material was formed required for late volcanism on the Moon.

 

 

Chang'e-5 was the fifth lunar exploration mission of the Chinese Lunar Exploration Program; it included a robotic lander which landed on the near side of the Moon. The mission brought back about 1.7 kg (3.7 lbs) lunar samples to Earth on 16 December 2020; the first samples collected from the Moon since 1976 with the Soviet Union’s Luna 24 mission. Chang'e-5 collected these samples using two methods, i.e., drilling for subsurface samples and scooping for surface samples. The Chang'e 5 landing site named Statio Tianchuan is in the Northern Oceanus Procellarum near a huge volcanic complex, Mons Rümker, located in the northwest lunar near side. This area is characterized by some of the youngest mare basalts on the Moon (~1.2 billion years old) which has never been sampled by Apollo or Luna mission. The maria region show much less cratering and thus must be significantly younger. Most of the large impact basins and the mare formed or basaltic eruptions flowed into the low elevations associated with the nearside impact basins by the end of the Imbrian period, some three billion years ago. However, Oceanus Procellarum (or The Ocean of Storms) does not correspond to any known impact structure and based on the method of crater counting the youngest mare basaltic eruptions are thought to have erupted 1 billion years ago. Volcanic activity has occurred within the Moon, but the results are mostly quite different from those on Earth. The lavas that upwelled in floods to form the maria were extremely fluid. Evidence of volcanic mountain building as has occurred on Earth is limited to a few fields of small, low domes. Several geologic provinces containing shield volcanoes and volcanic domes can be found within the near side "maria", such as on Mons Rümker (The Chang'e 5 landing site). Oceanus Procellarum is a 2500 kilometer wide stretch from the north to the south of the Moon and is very dark in color. This was china's first sample return mission and from this region it brought back 1.8 kilograms of rock. The analysis of this volcanic rock revealed that it was dated to about 1.96 billion years old which is surprisingly younger for volcanic rock. With the efforts of Chang’e-5 mission scientists were able to determine an eruption age for these lavas of 1.97 billion years, a whole billion years younger than any previously dated basaltic lava from the Moon. The rock shows that on the Moon there was volcanism for at least a billion years after we thought that it had already seized and so this is the youngest evidence of lava flow that is dated on the moon. Building on techniques developed in the 1970s for the analysis of the first Apollo samples researchers from China, Australia, Sweden and the US have been studying samples collected from the Moon by the Chinese National Space Agency during the Chang’e-5 mission. This is the result of new work from an international collaboration of planetary scientists published in the journal Science. A goal of the Chang'e-5 mission was to find evidence of some of the youngest volcanic eruptions on the Moon, thanks to samples that were retrieved by Chang’e-5 mission which tells us that there was lava flow a billion years after the period of what we thought end of lava flow on the moon. Lunar samples returned by the Apollo and Luna missions are all older than about 3 billion years, but samples returned by Chang'e 5 in late 2020 confirmed remote sensing analysis that rocks in the area were relatively young, at only 2 billion years old. Lava was still flowing on the surface of the Moon 1.97 billion years ago – and now we have the rocks to prove it; suggesting that either the Moon lightly cooled much later than we thought or that there is an entirely new explanation altogether for later volcanism on the moon.

 

 

Although the last volcanic eruptions on the Moon ended over three billion years ago, as most of the volcanic activity occurred between 3 and 3.8 billion years ago. Planetary scientists have confirmed this by dating basalts from the Apollo and Luna rock collections, as well as meteorites that originated from the Moon. In order for volcanic eruptions to occur, heat is required on the inside of a planet to generate the molten material involved in the process. We used to think that volcanism on the moon stopped at some point after 3 billion years ago. For a planet the size of the Moon, it is thought that this heat would have been lost long before these eruptions 2 billion years ago. So what’s going on? While scientists previously speculated that either a relatively high water content or the presence of high concentrations of radioactive elements in the lunar interior could have melted rocky material inside the Moon; heat-producing elements in the lunar interior that might have driven volcanism in a late stage of the moon's life in some areas. But new Chang'e-5 data published in Nature appears to have ruled out these hypotheses; the compositions of these samples indicate this was not the driving force in this case. It remains to be seen whether so-called tidal heating could have played a role, where heat was generated in the Moon’s interior by the stretching and squeezing (think of an elastic band warming up through friction as you stretch it) due to gravity between the Moon, Earth and Sun. Similar to what is happening on Jupiter’s moon IO as there is constant volcanism on it because of tidal forces, which is basically that IO is being flexed and pulled in all directions by gravitationally strong bodies around it which is Jupiter and its other large moons. The landscape is covered in craters that have been preserved because there is no atmosphere, and therefore no weathering, of the surface. Although scientists have previously been able to predict volcanic rocks of this age on the Moon by studying the number of impact craters on the lunar surface; based on the age-dating technique of "crater counting" the youngest basaltic eruptions are believed to have occurred about 1.2 billion years ago. It is impossible to confirm this without having samples to examine; scientists do not possess samples of these lavas. Until now though, younger volcanic rocks predicted by crater counting studies had remained elusive. An analysis of lunar samples returned by China's Chang'e 5 moon mission has produced a new possible answer for late volcanism in the moon's history. A new study led by Prof Chen Yi from the Institute of Geology and Geophysics of the Chinese Academy of Sciences provides an answer to the question of how young volcanism occurred on the moon. The researchers conducted a series of fractional crystallization and lunar mantle melting simulations to compare 27 samples of Chang'e 5 basalt clasts with Apollo basalts. They found that the young magma collected by Chang'e 5 had higher calcium oxide and titanium dioxide contents than older Apollo magmas. These are calcium-titanium-rich late-stage lunar magma ocean cumulates are more easily melted than early cumulates. The research presents evidence for the first viable mechanism to account for young volcanism on the Moon that is compatible with the newly returned Chang'e 5 samples and could help understanding of the Moon's thermal and magmatic evolution. In any case, this new work on Chang'e-5 lunar sample has therefore opened up a new scientific mystery of how a small rocky planetary body like the Moon could have retained enough interior heat to continue producing volcanic eruptions 2.5 billion years after it first formed 4.5 billion years ago. Work is now continuing on the samples to try to shed light on this question. Analysis of the samples took place using the sensitive high-resolution ion microprobe (SHRIMP) instrument, at the SHRIMP Centre in Beijing, China. The SHRIMP II instrument was used for dating the basalt chips. The process of determining the age of the rocks was complex; scientists used a focused beam of charged particles to eject material from various mineral phases in the rocks and analyzed the ejected material. Scientists in China manually picked out several tiny fragments of basalt (a volcanic rock), roughly 2 millimeters in size, for investigation. This was followed by laboratory analyses, building on techniques developed in the 1970s for the analysis of the first Apollo samples.

 

 

The Sensitive high-resolution ion microprobe (SHRIMP) was designed and constructed in RSES (Research School of Earth Sciences) of the Australian National University starting about in the late 1970s. It was to fulfill a need to be able to do isotopic analysis on in-situ on grains and solid materials that we could actually mount up or put into mounds which then ablated by a primary ion beam. It can measure the isotopic and elemental abundances in minerals at a 10 to 30 μm-diameter scale and with a depth resolution of 1–5 μm. The most common application of the instrument is in uranium-thorium-lead geochronology, although the SHRIMP can be used to measure some other isotope ratio measurements and trace element abundances. Zircons contain amounts of uranium and thorium (from 10 ppm up to 1 wt%) and can be dated using modern analytical techniques. Growing interest from commercial companies and other academic research groups, notably Prof. John de Laeter of Curtin University (Perth, Western Australia), led to the project in 1989 to build a commercial version of the instrument, the SHRIMP-II. The SHRIMP is primarily used for geological and geochemical applications. Fifteen SHRIMP instruments have now been installed around the world and SHRIMP results have been reported in more than 2000 peer reviewed scientific papers. Scientists take a very small sample with dozens of zircons in it and when they have these grains, they take these dozens of zircons to the iron probe. Ion probe like the SHRIMP look at their different growth structures inside each zircon crystal. So the SHRIMP iron probe measures the content of uranium and lead. When zircon crystallizes it incorporates uranium that over time decays to lead because we know the decay rate for uranium, we can convert the U/Pb ratio to an age. Since zircons have the capability to survive geologic processes like erosion, transport, even high-grade metamorphism, they are used as protolith indicators. One of the frequent questions is why is SHRIMP so big? Scientists explains it's big because we need to do two things, one is we need quite high mass resolution to be able to separate molecules which will interfere with the species we're after. The inclusions (particles of distinct composition embedded in rocks) are so difficult to access that it took decades of inventions until today’s state-of-the-art ion microprobe instrument. The second thing we're after is to be able to keep as many of the ions that are coming off the surface of the target through to the other end of the mass spectrometer, so that gives us our sensitivity and of course the sensitivity is what gives part of its name Sensitive High Resolution Ion Microprobe (SHRIMP). So the mass spectrometer is about seven meters in length, the magnet turning radius is one meter and those were almost an order of  magnitude larger than any instrument at the time. In Earth sciences, radiometric dating and the SHRIMP enabled the accurate determination of the uranium-lead age of the mineral zircon, and this has revolutionized the understanding of the isotopic age of formation of zircon-bearing igneous granitic rocks. SHRIMP is an important tool for understanding early Earth history having analyzed some of the oldest terrestrial material like the age of zircons from the Jack Hills. Also its significant milestones include the first U/Pb (uranium–lead date) ages for lunar zircon. Lunar granites are relatively rare rocks that consist of quartz, plagioclase, orthoclase or alkali feldspar, rare mafics (pyroxene), and rare zircon. U-Pb (uranium–lead) date of zircons from these moon rocks and from lunar soils have ages of 4.1–4.4 billion years.

 

 

SHRIMP is a very powerful technique  understanding what the abundances of isotopes of different elemental systems that not only tells  you about the pre-history of rocks on earth but upon analyzing the composition of the regolith on the Moon, particularly its isotopic composition, it is possible to determine if the activity of the Sun has changed with time. The gases of the solar wind could be useful for future lunar bases, because oxygen, hydrogen (water), carbon and nitrogen are not only essential to sustain life, but are also potentially very useful in the production of fuel. The composition of the lunar regolith can also be used to infer its source origin. Study so far interesting but it does not tell us how long ago the earlier version of the moonless Earth was formed, for that we need to date rocks to formed beyond the earth rocks that never went through the melt and re-hardening process like all the rocks on the earth and the moon; for this we need to examine meteorites. Similar sort of thing to look for like the jack hill zircons, we can go to a meteorite which is a sample of the molecular cloud or the material which formed our solar system and start trying to find grains  which actually pre-date our solar system. With various meteorite scientists are looking for variability in these isotopic compositions because it turns out different grains forming around different stars  will come out with different isotope compositions and these just are not subtle variations but scientists try to measure as accurately as possible on Earth, they see orders of magnitude variation, carbon and nitrogen isotopes of various grains. Scientists are looking for carbon and nitrogen isotopes because as it turns out one of the best ways of finding these grains in a meteorite is to digest the meteorite with acid. It's like finding the needle in the haystack first thing, so what you do is burn down the haystack to get rid of the haystack and then look for the needles that are that are left over. And so when scientists did this they found things like silicon carbide, graphite, diamond grains, they measured the isotope compositions of those grains and most of those grains in silicon carbide come from what are the red giants. So at the moment if you look up in the sky you will see the Orion the big red star, down the bottom is Betelgeuse and then there is Antares another red giant star. So there are a lot of these red giants which are the smoky and form these planetary nebulas; shells of dust coming out and so these are the source of the dust which actually forms our solar system. The Orion Nebula is one of the most studied regions of star-formation. The Orion Nebula appears to the eye as a tiny, hazy spot. But it's a vast stellar nursery, a place where new stars are forming. Four recently formed stars in the Orion nebula show what the solar system might have looked like at its birth some 4.6 billion years ago. Gravity collapsed dense globules of dust and gas into each of the four stars. Observing them we can find the bright glow in each image is the star, and the dark oval is the protoplanetary disk seen at an angle. Observations of this nebula have provided important new insight into the formation of stars and planets. The outer material formed into the surrounding protoplanetary disks, which are believed to be the precursors of planets. So we can tell that a lot of the material which forming our solar system probably came through that pathway of another star. We know out of the big bang we only have hydrogen and helium, and that we need stellar nucleosynthesis to form carbon, nitrogen; the elements have to be built in a violent explosion of stars called as a supernova event. These stellar events makes all the other elements that make us and make all the materials that we have around us, making up planetary objects. So we know that supernovas and kilonovas produce a  lot of material, supernova nucleosynthesis is the nucleosynthesis of chemical elements in supernova explosions. In sufficiently massive stars, the nucleosynthesis by fusion of lighter elements into heavier ones occurs during sequential hydrostatic burning processes called helium burning, carbon burning, oxygen burning, and silicon burning, in which the byproducts of one nuclear fuel become, after compressional heating, the fuel for the subsequent burning stage. In this context, the word "burning" refers to nuclear fusion and not a chemical reaction. In nuclear astrophysics, the rapid neutron-capture process, also known as the r-process, is a set of nuclear reactions that is responsible for the creation of approximately half of the atomic nuclei heavier than iron; the "heavy elements", with the other half produced by the p-process and s-process. Traditionally this suggested the material ejected from the re-expanded core of a core-collapse supernova, as part of supernova nucleosynthesis, or decompression of neutron-star matter thrown off by a binary neutron star merger. The relative contribution of each of these sources to the astrophysical abundance of r-process elements is a matter of ongoing research. In particular, studies of meteorites suggest that the solar system formed in a region similar to the Orion Nebula. Observing the Orion Bar is a way to understand our past. It serves as a model to learn about the very early stages of the formation of the solar system. So with SHRIMP scientists can study these grains and can see their signatures and isotope compositions and then tell everybody that what actually happened even before the start of the solar system formation.

 

 

The Apollo program was the political idea at first, the fact that USA were in a cold war with the Soviet Union who got to the moon first as they had a lander on the moon years before Apollo. So the journey to the moon wasn’t all about science at first; it began as a race between the US and the Soviet Union to build technology, and to prove their military supremacy to each other and the world. But moon rocks helped to change that as Apollo mission brought back moon samples, a scientific treasure trove. Those moon rocks are literally the part of our creation story. Scientists found the Moon rocks to be surprisingly perhaps disappointingly, like those on Earth. It turns out that the Earth and the Moon are chemically very similar indeed. The moon rocks revealed the biggest impact was the one that created the Moon itself and also helped scientists to decide the age of the moon that the lighter regions of its surface are over 4 billion years old. So we began to see space as a place for science and that the whole world could use and so by the end of the Apollo era, NASA were not only sending Air Force test pilots aboard Apollo mission rockets as astronauts but were sending scientists/geologists that changed NASA’s mission forever. So we had six successful landings that took 12 astronauts on to the moon and the last of those was Harrison Jack Schmitt. He was a Harvard graduate with PhD in geology and he was the only scientist amongst those 12 men to walk on the Moon. A geologist by training, Schmitt was hailed as the first Apollo “scientist-astronaut”, his selection was the culmination of a long-running campaign from the scientific community to send a geologist to the Moon. Now there is a dedicated team at the European Space Agency that teaches astronauts to identify geological features, so they can find the most interesting samples when they go to explore the moon with upcoming manned Artemis missions. This team also works with engineers and scientists to develop next generation tools to support the scientific exploration on the moon. So far what researchers have learned has been stunning like the Moon and Earth have a common ancestry. And because of the lunar rocks, we now know that the Moon is about 4.5 billion years old, around the same age as the Earth. But scientists believe there are still more secrets to be uncovered. The theories about the moon's formation and evolution are not perfect yet. It's difficult to answer how exactly the moon formed but thanks to lunar meteorites and returned samples scientists have gathered these hints. NASA reported the first step of mankind on the moon to be the single greatest technological achievement of all time. There are still so many things we don't know and lot to learn about the moon. Apollo missions were measured in days with their spacewalks limited to hours. Another trip and more moon samples from wider variety of locations might give us more insights. With Artemis program, we are looking to go and planning to stay on the Moon. The future Artemis missions will send astronauts back to the moon with advanced equipment and technology to look for more answers or perhaps more questions to answer that we don't know yet. NASA is not alone in this Moon rush. Private companies are sending robotic missions. Russia and China are collaborating on plans for a Moon base and space station. It’s not quite the Cold War, but the Moon gotten everyone’s attention. We are going to the Moon with the goal of establishing a human presence to learn how to live and work in deep space to prepare for the first human missions to Mars.

 

 

NASA’s current mantra for crewed exploration is “Moon to Mars.” NASA along with commercial partners and international Partners is working not only to land the first woman and first person of color on Moon but to establish the first long-term presence at the Moon as part of Artemis, also jointly to venture out into our solar system to explore, see and understand. Humans are the most fragile element of this entire endeavor, and yet we go for humanity. Today our calling to explore is even greater, we go to the moon together and on to Mars to seek knowledge and understanding for the benefit of all humankind. This time, we’re going to the Moon with the goal of establishing a human presence to learn how to live and work in deep space to prepare for the first human missions to Mars. By utilizing water ice on the Moon, NASA hopes to learn how to “live off the land” in an environment with a lot of radiation, vast differences in temperature, nasty dust, and more — training ground for living on Mars. Finding water on the Moon has the potential to be a game-changer. So from our scientific research we know that there are resources, the next we need to know that are they reserves? But what we do know is that they have the potential to enable not only human exploration with beyond low-earth orbit and on to Mars but the gateway to the solar system. We continue to build on the legacy of the Apollo program as the Artemis Generation prepares to go farther into the cosmos than ever before. To go farther, we must be able to sustain missions of greater distance and duration by using the resources we find at our destinations. Scientists, engineers and technocratic community are busy developing technologies that can overcome radiation, isolation, gravity, and extreme environments like never before. These are the challenges we face to push the bounds of humanity. Artemis program already started this journey with the Space Launch System (SLS), the most powerful rocket ever developed with the ability to get larger, heavier payloads off planet, and beyond Earth's gravity. We have Orion capsule, NASA's next generation human space capsule that can support humans from launch, through deep space, and return safely back to earth. This system is capable of being the catalyst for deep space missions; for next giant leap. On the next mission, Artemis II, SLS will launch Orion carrying a crew of four astronauts during which Orion will fly past the Moon and back, so Artemis II will be the farthest humans have ever traveled into space. On the Artemis III mission, SLS will launch with Orion taking four astronauts and cargo to study the Moon’s South Pole. The moon is quite uniquely suited to prepare us and propel us to Mars and beyond. We turn towards the Moon now, not as a destination, but as a stepping stone, as a checkpoint toward all that lies beyond. Our greatest adventures remain ahead of us that to prepare for humanity’s next giant leap, sending astronauts to Mars.

 

 

Now why is that important? There is one major threat to the propagation of the human species besides what we do to ourselves here on earth and that is the potential of a very large impact occurring on the earth something like what wiped out the dinosaurs. 66 million years ago, a mountain-sized asteroid traveling 10 times faster than a bullet from an assault rifle slammed into the shallow seas covering what is now the Yucatan Peninsula of Mexico. The immense energy of that impact hurled rocks as far north as Canada, and it vaporized the asteroid, part of Mexico and part of the shallow sea. This fireball of vaporized rock and water rose far above the earth's atmosphere and spread over the planet. As it cooled, molten drops of rock about the size of a grain of sand solidified into an immense swarm of shooting stars. The shooting stars re-entered the earth's atmosphere and heated the upper atmosphere to a thousand degrees Fahrenheit. Standing at the ground, the dinosaurs saw the blue sky become a sheet of red-hot lava. They broiled to death under the glowing skies. The energy in the sky is like that in the glow bar in an electric oven. The glowing skies started everything on fire. Great clouds of smoke rose into the upper atmosphere and blocked the sun. So that no sunlight reached the ground, it became cold and dark. Photosynthesis stopped, and plants and animals, in the ocean or on the land, either starved or froze to death. The dinosaurs didn't do anything wrong that caused their death. It was just fate that an asteroid hit the earth and killed 70% of the species that we know of on the planet. So sixty some five million years ago we really ought to be well dispersed throughout the milky way galaxy at the least by the time that happened, it would be a good idea to continue as rapidly as possible to develop the capability to not only to bring moon into our economic sphere of influence to settle on the Moon and Mars which are in our own solar system but to have the propulsive capability, the technological ability and the psychological capability to move on away from the solar system into other venues in space.