Frozen water discovered on the moon’s surface could be mined for fuel

The
moon as seen from space.

Alexander
Gerst/European Space Agency

• A new study suggests there are hundreds of spots where
  ice may be exposed on the surface of the moon.
• This surface ice appears to be trapped in shadowed
  craters at the lunar poles.
• Human or robotic missions could harvest such water and
  turn it into fuel for spacecraft.
• However, engineers 
  who study
  space mining say we need to send
  rovers into craters to find out how wide or deep the ice
  deposits go.

Shadowy craters near the moon’s poles may hide untold reserves of
ice — an incredibly precious resource in space — within reach of
robotic and human explorers.

That’s one big takeaway from a new study published Monday in the
Proceedings of the National
Academy of Sciences. The researchers took data from US and
Indian lunar spacecraft, then compared it to computer simulations
of how surface ice might look to those robots.

Their model detected hundreds of locations on the moon where ice
may lurk very close to or directly at the moon’s surface.

Leslie Gertsch, a geological
and mining engineer at the Missouri University of Science and
Technology, called the new data sophisticated and specific —
though not a surprise.

“This idea has been around for awhile,” Gertsch, who studies how
to extract resources in space, told Business Insider. “But this
study says, ‘yeah, there really does seem to be water ice at the
surface of the moon.'”

If true, these spots might be compelling places to mine the
moon’s ice deposits.

“There’s a need to know if there’s ice on the surface in order to
extract it,” Angel Abbud-Madrid, director
of the Center for Space Resources at the Colorado School of
Mines, told Business Insider. “This is one more step closer to
prospecting the moon and showing how accessible its ice is.”

Finding easy-to-extract deposits of lunar ice would do more than
give astronauts something to drink. Water can be split into its
atoms — hydrogen and oxygen — which could make a fuel for rocket
engines that could power a new era of space exploration.

“Extracting ice from the moon would be a first step in building a
space economy,” Abbud-Madrid said.

But both researchers, neither of whom was involved in the study,
say people and robots are not quite ready to start mining the
moon yet.

Mapping the moon’s icy cold traps

A
map of “cold traps” inside lunar craters at the moon’s north pole
(left) and south pole (right). Green and teal dots show locations
where water ice may be present at or near the
surface.

PNAS

The moon — an airless, 4.5-billion-year-old rock — is a terrible
place to be if you’re surface water and want to stick around for
awhile.

Daytime temperatures on the moon can soar to hundreds of degrees,
and ice exposed to a vacuum will sublimate (or turn directly into
a gas) with the least bit of jostling or warmth.The process is
similar to how dry ice, or frozen carbon dioxide, slowly vanishes
when exposed on Earth. A “wind” of particles from the sun blows
any free gases on the lunar surface out into space.

However, since at least the 1950s, researchers have speculated
about the existence of “cold traps” in permanently shadowed
craters on the moon. Such regions are so cold that they keep any
water there frozen, and might even freeze water vapor that passes
by — in the same way a freezer pack attracts a coating of frost
on a humid day.

The idea of these cold traps has gotten a boost in recent
decades, thanks to moon-orbiting spacecraft like NASA’s Lunar
Reconnaissance Orbiter (LRO) and India’s Chandrayaan-1. A probe
called the Lunar Crater Observation and Sensing Satellite
(LCROSS) even smashed into one of these craters and tossed up the
dirt to see what was there.

“They found water, they found mercury — all kinds of cool things,
and more than usual,” Gertsch said.

However, that probe didn’t find out how close to the surface
water might be. The results of the new study hint that about 3.5%
of lunar cold traps may have ice exposed at the surface, perhaps
as a frost. But there’s still no estimation of the depth of the
prospective ice deposits.

“When people think of the tip of an iceberg, they think it’s much
bigger underneath. That might not be the case here,” Gertsch
said. “It could be the tip of an iceberg. But if we’re talking
about frost, it could be a very, very small iceberg.”

To figure out what’s there — and what isn’t — Abbud-Madrid and
Gertsch say we need “ground truth.”

“We need to send a little rover down, better yet a few, and poke
into some of these partially and permanently shadowed regions,”
Gertsch said. “We actually go there and drill down to see how far
down and how wide the deposits go.”

A rover could also assess the quality of the ice. If it’s pure,
it could be easy to extract. But if it’s mixed in with lunar
soil, called regolith, mining could prove more challenging.

How to mine the moon

An illustration of NASA’s
now-cancelled Resource Prospector rover mission to the
moon.

NASA

Assuming there is enough lunar surface ice to mine, harvesting it
won’t be straightforward. Just bumping into some lunar ice and
exposing it to the vacuum of space can make it vanish.

“Digging and carrying ice to some processor may not be the best.
You’d lose a lot of it,” Gertsch said. “Nobody is really thinking
about that, and they should.”

During a June meeting at the Colorado School of Mines, several
researchers met to brainstorm methods of mining the moon.
Abbud-Madrid discussed using three solar reflectors (basically
giant mirrors) to extract lunar surface ice with hardly any
digging at all.

“You redirect that energy to the surface, inside tents,” he said.
“It will hit the ice and sublimate it inside the tent.”

From there, a cold-trap effect would collect the water vapor,
then move it to a processing plant that would use electricity to
split the water into hydrogen and oxygen, separate them, and
store them as liquids.

“By doing that you will have the hydrogen and oxygen prepared for
a rocket that can land there,” Abbud-Madrid said.

But he added that extra fuel could even be stored in tanks and
lifted into orbit around the moon.

“You start making gas stations in space. This really starts
cutting your dependence on bringing all that fuel from Earth,” he
said. “That’s really been what’s holding us back from deep-space
exploration.”

But no mineral deposit is 100% guaranteed. Even on Earth, Gertsch
said, humanity’s record for starting a productive and
long-lasting mining operation is poor. For every successful
prospect, she said there are between 500 and 10,000 failures.

“We have different techniques today and can make use of better
information,” she said, adding that today’s advanced electronics
are better than prospecting methods used in the past. “But it’s
still not easy.”

The 239,000-mile distance to the moon, the vacuum of space, and
high radiation levels only raise the stakes.

Many researchers see asteroids or comets as another option for
mining, but they’re much farther away and move around. So
Abbud-Madrid said mining the moon makes a lot more sense — if it
has accessible water deposits.

“The moon is close. It’s right there,” he said. “You could even
mine it via remote-control.”