Thanks to our friends at Minute Earth for supporting this episode of SciShow.
You can click the link in the description to check out their new book,
it is absolutely wonderful; MinuteEarth Explains: How Did Whales Get So Big?
And Other Curious Questions about Animals, Nature, Geology, and Planet Earth.
[♪ INTRO]
The Apollo missions of the sixties and seventies inspired millions of people to
become scientists and engineers, but the astronauts who landed on the Moon
also came home with something far more tangible:
382 kilograms of Moon soil, also known as regolith.
Some of those samples have been lost or stolen since then,
but most were studied with the best technology of the time.
And 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 seventies could not.
And, well, welcome to the future. It is time to look at some Moon rocks.
Most of the samples brought home by the Apollo astronauts
were studied decades ago, answering countless questions
about the Moon’s age, origins, and history.
Questions like why do we have a Moon in the first place?
Scientists found that the oldest Moon rocks were a little younger than
the oldest stuff in the Solar System, and that they looked
a lot like what’s in the Earth’s mantle.
These observations helped lead to the Giant Impact Hypothesis:
The idea that a young, moonless Earth collided
with something about the size of Mars.
That crash launched a whole bunch of the crust and mantle into space,
which clumped together into what we know today as the Moon.
Other scientists discovered lots of natural glass in the Moon rocks that are
billions of years old, something that cannot happen on Earth because
the water in our rocks tends to break down glass in those rocks over time.
This made scientists think that the Moon rocks had almost no water in them.
And when they checked, those rocks looked bone dry.
So everything seemed to fit together.
Now, water is a good example of why we held some samples back from testing.
Before Apollo, many scientists believed the Moon would be pretty wet.
But by 1984, a NASA report confidently stated:
“We now know that hypothesis to be completely false.”
Except, within the next 15 years, radar signals from two separate satellites
revealed evidence of at least some ice trapped
in the rocks near the Moon’s south pole.
Other evidence from satellites and telescopes has only
gotten stronger over the past almost thirty years.
Today, everyone still agrees: The Moon is way dryer than Earth.
But the picture is definitely muddier than it used to be.
Which 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.
The good news is that these sealed samples give us
new ways of answering those kinds of questions.
In 2019, scientists from the Apollo Next Generation Sample Analysis Program,
or ANGSA, got ready to study untouched Moon rocks
for the first time in over forty years.
So the ANGSA group looked at a tube of material
collected on Apollo 17 by astronaut Gene Cernan.
He stuck the tube into the ground, so the Moon’s surface is at the top,
followed by about twenty centimeters of whatever was underneath.
That tube was sealed and brought back to Earth,
X-rayed, and then stored for decades, until 2019.
The hope is that scientists can use this sample to see how the surface
has changed over time, just like geologists on Earth
study rock layers to learn about an area’s history.
Now, back when the tube was first X-rayed, we got this picture of what’s inside.
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 the kind of improvement we’re talking about here.
Then, the tube was opened, and the sample was
split up so that it could be studied in a bunch of different ways.
That was late 2019.
Just like the rest of us, ANGSA had big plans for 2020, including opening another
sample that might have some of the Moon’s super-thin atmosphere trapped inside.
But like the rest of us, those plans were…delayed.
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.
They'll also be looking for evidence of amino acids in the samples,
to try to figure out if previous results of amino acids in regolith
are original to the moon, or an example of cross-contamination.
Opening that second sample was also delayed,
but other groups are hard at work understanding what’s going on in there, too.
It’s the same core as the other one, but from lower down,
so it should let scientists investigate even farther into the Moon’s past.
And if there really is some atmosphere trapped in there, scientists may learn a lot
about how the Moon’s surface interacts with the solar wind,
micrometeoroids, and the other ravages of outer space.
But, you may be asking yourself, why open it now?
Yes, our technology is better than it was in the seventies,
but it’ll probably be even better in the 2040s.
Well, it’s partly because between China’s robotic missions
and NASA’s Artemis program, there’s a lot of interest in the Moon lately.
And knowing whether there’s water on the Moon
would help us know how to sustain a colony up there someday.
Because water isn’t just water.
It’s also hydrogen and oxygen: Breathable air and rocket fuel.
So now is as good a time as any to open those samples up
and learn whether water, and any other exciting discoveries,
that can tell us about the Moon’s past, or our future, are up there.
Now is also a great time to buy a book for the young one in your family
and our friends at Minute Earth can help with just that!
This book answers children’s most curious questions like
“Where Earth’s water came from” and “Why leaves change color in the fall.”
And all of it is accompanied with gorgeous illustrations.
You don’t have to inspire curiosity in a child.
They are naturally curious.
All you have to do is respond to it with great resources like this one.
And often times you can find yourself learning along side them;
not just about the world, but also about the kid.
If you like what you see and you’d like to snatch a copy of this book,
you can head to dftba.com/collections/minuteearth
or you can just click on the link in the description.
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