Astronomers announced the discovery of water on the Moon, and we're gonna learn
more about it starting right now. Welcome back to Launch Pad Astronomy, I'm
Christian Ready, your friendly neighborhood astronomer, and in this
video we're going to talk about water ice that's been discovered in the
bottoms of craters on the Moon. The water and the craters are located near the
poles of the Moon, and this is important because at this location the Sun angle
is always very low. That means that sunlight never directly hits the bottom
of the craters and the temperatures in these regions never rise above -163°C.
For this reason, these locations are called "cold traps", and it's
inside these cold traps that water ice was detected. Now water has already been
detected in the cold traps of planet Mercury and dwarf planet Ceres.
However there haven't been direct observations of water on the Moon's cold
traps until now. Now the whole idea of water on an airless world is still
pretty strange. After all, daytime temperatures on the Moon reach 100°C.
That is, by definition, the boiling point of water. And because
the Moon doesn't have an atmosphere, ultraviolet radiation from the Sun would
easily break apart the molecular bonds of hydrogen and oxygen, and they would
just escape into space because the Moon just doesn't have much gravity. So
finding water on the Moon means that you've got to go looking in locations
where it can remain frozen solid as ice. And that's where these cold traps come
in. They're plunged into perpetual darkness, and any water that ends up
inside them is trapped. But how does water get inside a cold trap? Well, water
comes to the Moon the same way it came to Earth; delivered by asteroids and
comets coming in from the outer solar system. Now water has been detected on
the Moon before, at least indirectly. And sometimes there was a chance that
the hydrogen and oxygen didn't so much represent water, but represented
something else like hydroxyl. But this time the observations are direct and
definitely show the signature of water. The team used data from the Moon
Mineralogy Mapper or M3. M3 is a NASA-built instrument that
hitched a ride on India's Chandrayaan-1 spacecraft. Chandrayaan-1 launched to the
Moon in 2008 and observed the Moon for about a year before losing contact in
2009. Still, that was enough time for M3 to sample the entire lunar surface
including the polar regions. M3 is a spectrometer. That means
it takes light and spreads it out according to its color or wavelength. M3
was measuring infrared sunlight reflected from the Moon. Infrared is
important because water has a tendency to absorb certain colors or wavelengths
of infrared. That means that if there is a sample of soil, there should be no
absorption of infrared at these wavelengths. But infrared light coming
from some of the cold traps showed the unmistakable signatures of water
absorption. Now you may be wondering how M3 can detect reflected sunlight coming
from cold traps when by definition the Sun never directly shines there? However,
sunlight does reflect off of the crater walls, which in turn reflect to the
bottom of the crater and up to the spacecraft. So it's a very tiny amount of
sunlight, but it is enough for M3 to make some remarkable findings. First of all, it
found that most of the water ice exists in cold traps within about 20 degrees of
the Moon's two poles. Also, most of the ice is located in the Moon's southern
polar regions, and that makes sense because the craters down there are
larger and deeper. But what's really interesting is that of all of the
locations where water could exist, ice was only detected in about
3.5% of all of the traps. Not only that, but the craters
that actually did contain ice were older than about 2 billion years. That's very
interesting and tells us something about the history of the Moon's formation. You
see, about three and a half billion years ago, the Moon underwent a period of heavy
bombardment. Massive asteroids smashed the Moon on one side, liquefying its
interior. As it erupted as molten lava, that lava distributed
self to form the Maria that we see today. But it also had the effect of
hollowing out one side of the Moon's interior.
This caused the Moon to wobble a little bit, and it's starting around two billion
years ago, new cold traps began to form. But maybe there just hasn't been enough
time for ice to accumulate there yet. But there's something else that's really
cool about the story. Water is used to make rocket fuel!
Getting water off the Earth is very difficult and very expensive. Lifting it
off the Moon on the other hand is quite a lot easier. That means that our
nearest celestial neighbor can serve as a fuel depot for potential human
expansion into the solar system. It's nice to know that there's yet another
reason to go back to the Moon and I hope we can do that someday soon. By the way,
speaking of water, did you know that they discovered water in a lake underneath
the surface of Mars? Oh and speaking of Moons, did you know that they found 12
new Moons around Jupiter? I'll have links to those videos in the
description below. And if you have any comments or questions or anything you
want to say, please let me know in the comment section and I'll be sure to check
them out. And if you'd like to join me on this journey through this amazing
universe of ours, please make sure to subscribe and ring that notification
bell so that you don't miss out on any new videos. Until next time, I'm Christian
Ready, and keep watching the skies. [BEEP] This is direct detection of water at the
bottom of the Moon. Dammit! (laughs).
[BEEP] (cicadas singing loudly...) [BEEP]