Thanks to Skillshare for sponsoring today’s video. The Moon has always been
an object of fascination for mankind. It’s a prominent view in our night sky, a moon
massive and close enough that its beautiful and eerie details are visible with the naked eye.
Mankind stepped on the moon over 5 decades ago, but to this day, there’s still so much we don’t
know about it, and that’s why we keep going back and keep exploring. While the Moon seems like a
very different place from Earth, there’s one thing that excites scientists about future colonisation
prospects – there is increasing evidence of water on the Moon! I’m Alex McColgan and you
are watching Astrum. Join with me today as we follow the progress numerous space agencies
around the world have made to find out once and for all whether the Moon’s surface contains water.
Luna 24 was an ambitious robotic probe of the Soviet Union in 1976.
It successfully landed on the Moon, drilled into the lunar surface about 2 metres deep,
and sent about 170gs of lunar soil samples back to Earth.
Of greatest surprise to the scientists was the detection of water within the returned sample.
Around 0.1% of the sample was water, and they found that the concentration of water increased
with depth. However, like the very trace amounts of water detected in samples obtained during
earlier Moon missions, for example Apollo 11, this was assumed to be contamination from Earth.
The question whether there is water on the Moon remained unanswered.
In 1994, NASA’s Clementine mission showed that permanently shadowed areas,
that haven’t received any sunlight in billions of years, do exist near the Moon's South Pole.
As a result of this, there was a lot of excitement in the science community about whether there could
be frozen ice at the bottom of these craters, protected from the harsh rays of the Sun,
where the temperatures would never rise above about -173 °C (-280 °F). Any water ice at the
bottom of these craters could probably exist indefinitely at these temperatures.
Excited by this discovery, NASA launched the Lunar Prospector spacecraft shortly afterwards in 1998,
specifically to hunt for clues that water may exist there.
While it didn’t give us any conclusive answers to the mystery, it certainly added to the intrigue.
The Lunar Prospector detected large amounts of hydrogen at the Moon’s poles using spectroscopy
from orbit. Data from Prospector suggested that there could be somewhere between 10 to 300
million tons of water-ice scattered inside craters around the lunar poles.
But large amounts of hydrogen do not necessarily mean the presence of water,
it could also be water’s closest chemical relative, hydroxyl (OH). The Prospector spacecraft
subsequently crashed into the Moon's South Pole in 1999, with NASA scientists hoping the impact
would blast ejecta into space, lit up by the Sun, so that scientists could use spectroscopy to prove
the existence of water in the dark craters of the Moon using Earth based telescopes. Unfortunately,
no water ice was detected from the Lunar Prospector’s impact. The mystery continued.
Japan’s SELENE or Kaguya spacecraft was launched in 2007, and its mission was to take high
resolution images of the Moon and map the lunar surface. But it also wasn’t able to detect any
signs of water ice in permanently shaded craters around the South Pole of the Moon, so after 18
months of orbiting, it too purposefully crashed into the Moon, hoping that this time it would
release enough ejecta into space for Earth based observatories to work with. But again,
no evidence for water was found. In 2008, India’s first moon mission - Chandrayaan-1 - was launched.
Chandrayaan-1 was different from previous missions in that instead of relying on sensors
to detect water from a distance, India included an impactor that could specifically detect water
in its gaseous form through spectroscopy as it came in close proximity to the spacecraft.
Scientists believed water vapour could be in the extremely tenuous atmosphere of the Moon
just above these craters. The impactor probe was released from the main body of the spacecraft
and descended for 25 minutes before it crashed near a crater at the South Pole of the Moon.
As it descended, it sent the data back to the Chandrayaan-1 mothership, and within that data
was the answer scientists had been looking for all these decades: a confirmation of water!
And a few months later, the Moon Mineralogy Mapper instrument aboard Chandrayaan-1,
using spectroscopy from orbit, also detected the presence of water on the Moon!
But NASA wanted more proof. They launched their own Lunar Crater Observation and Sensing Satellite
mission as well as the LRO, an orbiter you will be very familiar with if you follow this channel.
LCROSS was a simple, low-cost, fast-track mission, and it had one main objective,
which was to once and for all confirm the presence or absence of water ice in a permanently shadowed
crater near a lunar polar region. It had a simple, straight forward, yet very clever design.
In an unusual move, the first stage of the Atlas-V rocket LCROSS was launched from stayed attached to
the spacecraft and upon reaching the moon, it was released to crash into one of the dark craters at
the South Pole of the Moon. This impact was similar to how Lunar Prospector and Japan’s
Kaguya probes crashed into the moon to eject a debris plume that rose above the lunar surface,
but unlike them, the LCROSS spacecraft itself flew through the debris and collected data
without relying on Earth based observatories which clearly weren’t very reliable for studying small
plumes of debris. As the debris cloud rose above the crater’s rim, and was exposed to sunlight,
any water ice and other molecules of interest were vaporized and broken
down into their basic components which the sensors onboard LCROSS were able to detect…
only for it to crash into the Moon too, after accomplishing its task. This combination of
collisions produced a large plume of surface material which the LRO was left to study.
The data sent back from this mission showed that the lunar soil within shadowy craters is rich in
useful materials, such as hydrogen gas, ammonia and methane, which could be used to produce fuel
for space missions. And it even settled the debate of whether water was present as the data heavily
suggested that hydrogen found at the lunar poles does indeed belong to crystals of water ice!
And it doesn’t stop there, recently NASA’s SOFIA (Stratospheric Observatory for Infrared Astronomy)
discovered water on the sunlit surface of the Moon. Its data suggests that water on the Moon may
not be just limited to cold and shadowed places but may be distributed across the lunar surface.
SOFIA has found that the Clavius Crater, one of the largest craters visible from Earth,
has water in concentrations of 100 to 412 parts per million. To put that into perspective,
the Sahara Desert has 100 times the amount of water than what SOFIA detected in the lunar soil.
So yes, that is an astonishingly low quantity, and it might not be of much use to us, but it
helps us in learning about the lunar surface and how it works. It raises questions like how
water is created and how it persists on the harsh, airless lunar surface. Without a thick atmosphere,
water on the sunlit surface should just be lost to space. Yet somehow there still is some water.
Something is either generating the water, or something must be trapping it there.
There are several hypotheses as to why this might be happening.
Micrometeorites raining down on the lunar surface,
carrying small amounts of water, could deposit the water on the lunar surface upon impact. Another
possibility is that a two-step process whereby the Sun’s solar wind delivers hydrogen to the surface
and causes a chemical reaction with oxygen-bearing minerals in the soil to create hydroxyl.
Meanwhile, the bombardment of micrometeorites could be transforming that hydroxyl into water.
It could then be trapped into tiny beadlike structures in the soil that form out of the high
heat created by micrometeorite impacts, or the water could be hidden between grains of lunar soil
and sheltered from the sunlight. Water is known as the “the oil of space” and finding
a successful and affordable way to mine it on the Moon would be game changing in the space industry.
It can be recycled inside a lunar habitat and used for drinking water or washing. It could also
be used to help plants grow on the Moon, which are needed to nourish future lunar colonists.
But the biggest and most immediate application for lunar water is making rocket propellant. Hydrogen
and Oxygen are two of the biggest materials that are used to power rockets right now.
You see, getting stuff into space from Earth is a very fuel intensive and expensive process. And the
deeper into space you want to go, the more fuel you need, and the more fuel you have to carry.
Having to bring all this from Earth heavily limits space exploration.
But the Moon has 1/6th of Earth’s gravity, so if we are able to successfully produce rocket
propellent on the Moon, it’s less resource intensive and transporting propellant from the
Moon to other locations in space would be nowhere near as expensive as transporting it from Earth.
And actually, getting something from the Moon to low Earth orbit, is less resource intensive
than sending it from Earth itself - even though that adds 300,000kms to the journey.
So, the presence of water on the moon could help make space missions
more affordable and dramatically increase our capabilities of exploring the solar
system! Now, NASA’s Polar Resources Ice Mining Experiment-1 mission is coming up,
and it is expected to launch in December 2022. We know water-ice exists in some of the dark craters,
but does it exist in all of them? The objective of the PRIME-1 mission
is to land a drill and mass spectrometer near the South Pole of the Moon.
Similar to PRIME-1 is ESA and Roscosmos’ PROSPECT mission, which, should this mission still go
ahead, is scheduled to be launched in 2023, and it too will drill beneath the surface in the
South Pole region of the Moon and extract samples, expected to contain water ice and other chemicals.
This will test processes that could be applied for resource extraction in the future.
India is also planning to launch Chandrayaan-3 its third lunar mission in August 2022.
But most interesting of all is NASA's Artemis lunar rover, the Volatiles Investigating Polar
Exploration Rover, or VIPER, the first-ever resource mapping rover on another celestial body.
It is planned to be launched in November 2023 and will explore the relatively nearby but
extreme environment of the Moon first hand in search of ice and other potential resources.
It will help us find where the Moon's ice is easiest to access
and most likely to be found. The first resource maps of the Moon will mark a critical step forward
for NASA's Artemis missions to establish a long-term presence on the surface of the Moon.
So, there we have it. Almost everything you would want to know about water on the Moon.
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