Lunar Liquid

by Molly Bentley on October 25, 2010

It’s a big story in the Washington Post: there’s water on the moon.

Now mind you, there’s been a suspicion of water — in the form of hard ice — on this otherwise dusty, airless satellite for many years now.

Radar signals bounced off the Moon pointed to ice huddled in the shadowy craters of the south polar region.    It was a strong hint that reserves of H2O lurked here, in dark places where the Sun never shines.

NASA’s LCROSS mission has confirmed the suspicions. LCROSS did this by throwing some rocket hardware at the moon, and then quickly sampling the plume of debris kicked up by the collision.

The water is in the form of ice that’s far colder and harder than the cubes in your fridge, but there’s enough of it to supply both sustenance and possibly even rocket fuel for future lunar settlements. In case you wonder where the water comes from, the most plausible scenario is that it’s remnant material from comets that occasionally slam into the Moon.

This “exploration by collision” has worked so well, it gives more credence to an idea once floated by NASA scientist Chris McKay for searching for life on Jupiter’s icy moon, Europa. Those of you who follow such things are undoubtedly aware that Europa is covered in a shell of ice perhaps 10 miles thick, under which — we think — is a sixty-mile deep ocean of liquid water. Could there be some sort of life swimming in this unseen sea?

One way to find out would be to “throw a bowling ball at Europa”, in the words of McKay. This would be done with a robotic spacecraft, of course.   The bowling ball would be followed by a “catcher’s mitt” that would collect the icy debris kicked off the surface.   This material would then be analyzed, and maybe — just maybe — there would be some organic bits and pieces in that surface ice that have had slowly eased their way up from the ocean below.

It worked for the Moon. Maybe a similar experiment at Europa could prove that there’s biology elsewhere in the solar system.  That would be even more interesting than hard ice. – Seth

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{ 5 comments… read them below or add one }

avatar Tim Mundorff October 25, 2010 at 12:20 pm

I’m wondering if anyone has done a spectral analysis of the light reflecting off the surface of the surface of Europa and what that might tell us.

avatar Cynthia Phillips October 25, 2010 at 9:37 pm

Great question, Tim! Actually, a spectral analysis is how water ice was found on Europa’s surface in the first place – before Europa was ever visited by a spacecraft, ground-based observers using telescopes on Earth detected the unique spectroscopic signature of water on Europa, suggesting an ice-covered world. Today, we can use spectroscopy from the Earth and from orbit to help better understand the surface composition of Europa. So far, we’ve found carbon dioxide, sulfur dioxide, and some weird compounds that are thought to be either sulfuric acid or hydrated salts.

avatar Daniel Spain October 26, 2010 at 7:07 am

I’m excited at the increasing rate of discovery today.
Water on the moon, extrasolar planets, and many other amazing things people a few decades ago could only dream of!
I think the discovery of microscopic extraterrestrial life will be coming soon. I can’t wait to see that!

avatar Molly Bentley October 26, 2010 at 8:09 am

Editor’s note: Cynthia Phillips, who commented above, didn’t mention this – but she’s a astronomer who processes images of planets and other bodies, with particular focus on Europa.

avatar Steve Bergman November 2, 2010 at 9:52 am

Cynthia Phillips said:

“””
So far, we’ve found carbon dioxide, sulfur dioxide, and some weird compounds that are thought to be either sulfuric acid or hydrated salts.
“””
If you are still following this thread, how much more do you think we might learn regarding Europa from, e.g. the future James Webb Space Telescope and the Thirty Meter Telescope, etc. before the Europa Jupiter System Mission arrives in the system (hopefully!) in ~2026?

Carbon dioxide? Sulfur dioxide? sulfuric acid and/or hydrated salts? I’m being highly (wildly?) speculative, of course. But I can’t help imagining the possibility of some archaea-like organism at work there. Similar to archaea here on Earth which live in micro habitats of liquid water in glaciers, created by their secretion of antifreeze proteins. Or archaea which oxidize sulfur compounds to extract energy.

Perhaps we won’t have to drill down 15 kilometers to find living things on Europa?

Another idea I have heard for exploring Europa’s ocean is to take advantage of the cracking of the ice (caused by tidal forces, I think). Those would be the places that the water which was most recently in liquid form might be exposed.

That’s where we would be most likely to find the most recently deceased life. But perhaps such a target is implicit in Chris McKay’s proposal.

-Steve Bergman

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