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 12th December as Uhuru Satellite day, though it is quite
significant date in science and astronomy community as 52 years ago on 12th
December 1970, the first satellite launched specifically for the purpose of
X-ray astronomy from the San Marco platform in Kenya. On 9th
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 13th
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 20th 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 20th 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.
No comments:
Post a Comment