LCROSS finds lots of fluff

[neufer]

LCROSS finds lots of water in accessible places
at the Moon's south pole -- but we'll have to tread carefully
The Planetary Society Blog By Emily Lakdawalla
Oct. 21, 2010 | 16:03 PDT | 23:03 UTC

Diviner map of the temperature of the Moon's south pole LRO Diviner Lunar Radiometer Experiment surface temperature map of the south polar region of the moon. The data were acquired when south polar temperatures were close to their annual maximum values.

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Fitting a spectrum

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<<It is an "opportunity for the future": an intentional crash landing onto a permanently shadowed crater on the Moon has produced evidence of large deposits of water. And that's not all. The water is accompanied by other volatile materials like ammonia, formaldehyde, and mercury. It is most likely held within a "fluffy" lunar soil that would be easy for future explorers to dig into. And these deposits probably extend beyond the Moon's permanently shadowed spots into "permafrost" deposits in sunlit regions that would be much more benign environments for exploration by robots or humans than the cold, shadowed places.

David Paige went first, explaining the mapping of the temperatures at the lunar poles using the Diviner instrument on Lunar Reconnaissance Orbiter.
This map shows that places on the Moon are very, very cold. 100 Kelvin would be cold enough to trap water for billions of years. But there's at least one spot that's only 29 Kelvin, which is the coldest place ever directly measured in the solar system. (Such temperatures are theorized to exist in places like the Kuiper belt but have not actually been directly measured.) So water's not the only thing that's stable for billions of years; many other things are too, what Paige called "supervolatiles," stuff that's even more ready to vaporize than water. These materials include methanol, ammonia, sulfur dioxide, formaldehyde, carbon dioxide, and hydrogen sulfide.

Igor Mitrofanov, representing the Lunar Exploration Neutron Detector instrument on Lunar Reconnaissance Orbiter. He said his instrument suggested that the soil within Cabeus' permanently shadowed regions may be up to 4% water by weight. This is important, as Tony Colaprete explained later, because about 1% water by weight is what's currently considered the floor for an abundance that is viable for extraction (not necessarily economically viable, just that if there's less than 1% water you end up spending more energy than you generate by attempting to extract it). More importantly, Mitrofanov argued that the "blue regions" in his data, indicating the presence of relatively large (by which I assume is meant, more than 1%) deposits of hydrogen in the lunar subsurface extend beyond the permanently shadowed areas, into sunlit areas at the poles. The upper few centimeters of lunar soil appears to be insulating the material below it, preventing the volatiles from warming enough to escape. "We may have enough amount of water outside of the permanently shadowed regions, which is very important for future exploration." Permanently shadowed regions are so cold that it would be difficult to operate there; if we can access water from sunlit regions, it would be much, much easier to deal with technologically, for both humans and robots.

Peter Schultz explained [that] the shape and speed of that plume was unusual. Normal impacts send things out instead of up, he said. But this one sent most ejecta straight up, and it was sent up at high speed. There were two reasons: one, the impactor (the Centaur stage of LCROSS' launch rocket) was hollow, and two, the material that the Centaur slammed into was very, very fluffy. I actually called Pete (from whom I took a class on impact cratering a long time ago) to ask him about this fluffiness. Was it fluffier than what the Apollo astronauts walked on? He said yes, much fluffier. He said when you simulate impacts into Apollo-landing-site-like dust, you see an impact flash within nanoseconds. But LCROSS did not see any visible flash of light until 0.3 seconds after the impact. This is a really, really long time and indicates that before material got hot enough to emit that visual flash, it was being compressed. A lot. I joked with him that maybe this material really could swallow astronauts whole, which was a concern about the lunar dust before the first Moon landings, and Pete said that it really might. In fact, this material is so fluffy that it is a lot less like what we usually think of as lunar dust, and much more like the fairy-castle fluffy surfaces we imagine exist on the surfaces of comets.

Next up was Randy Gladstone, whose Lyman Alpha Mapping Spectrometer found evidence for molecular hydrogen, carbon monoxide, atomic mercury, calcium, and magnesium. There was quite a lot of molecular hydrogen, actually. He said this confirms that the lunar poles are excellent cold traps not just for water but for many other volatiles as well, and he mentioned that things like molecular hydrogen and mercury are useful for resource utilization -- that is, future human explorers.

Rich Vondrak presented more results from Lunar Reconnaissance Orbiter, and talked a bit further about how the crater appeared to be releasing water vapor gradually continuously for the entire four-minute descent of the LCROSS spacecraft following the Centaur impact -- in effect, it was "steaming."

However, in my conversation with Pete later, I learned that this ease of accessing the water cuts both ways. I asked Pete what would happen if you stuck a shovel into an area of the type that Mitrofanov was talking about, a place that is not permanently shadowed, where there is ice-bearing material a few centimeters below the surface. Pete said, first of all, that despite all the results shown today we don't really know what things look like much below the surface; all the material that got lofted upward was likely from pretty close to the surface, and the higher things went, the closer it was to the surface when it started. It could be a veneer of material, but we don't know if it's a veneer or not. It's quite possible that it goes very, very deep, and if so, it could be very, very old -- possibly old enough for these deposits to preserve volcanic gases left over from the later stages of the Moon's geologic activity. Secondly, he said, this material is probably so delicate, that even sticking a shovel into the ground might warm it enough to make the water and other, even more volatile stuff (like molecular hydrogen and ammonia) go away -- just the shovel will warm it up.

This fragility makes Pete worry about how these possibly commercially useful deposits of material are going to be approached next. "We don't want Captain Kirk to land there and step out and blow everything away," he said. Even a robotic lander, just by landing, could destroy the materials it was sent to observe. There may be something very ancient held within these deposits of cold materials. He likened it to the thousand-year-old giant sequoias in Redwood National Park -- you wouldn't study them by cutting them down. But just like an old-growth forest, it's a place where commercial interests and the interests of scientists to preserve an ancient and fascinating landscape may not be in alignment. For his part, Pete argued that before commercialization begins, we need to understand it better, otherwise we risk destroying something special.>>

[Ann]

Wow. Endangered lunar ice covered by puffs of fluff.

Ann

[bystander]

LRO detects surprising gases in impact plume
Soutwest Research Institute | 21 Oct 2010

It’s Cold and Wet at the Moon’s South Pole
University of Arizona | 21 Oct 2010

Lunar Impact Uncovered More Than Just Moon Water
NASA Science News | 21 Oct 2010

LRO Supports Historic Lunar Impact Mission
NASA | LRO Mission News | 21 Oct 2010

LCROSS and LRO Science Science Results of Lunar Impact
NASA | LCROSS Mission News | Media Telcon | 21 Oct 2010

Detection of Water in the LCROSS Ejecta Plume - A Colaprete et al

• Science 330 (6003) 463 (22 Oct 2010) DOI: 10.1126/science.1186986

The LCROSS Cratering Experiment - PH Schultz et al

• Science 330 (6003) 468 (22 Oct 2010) DOI: 10.1126/science.1187454

LRO-LAMP Observations of the LCROSS Impact Plume - GR Gladstone et al

• Science 330 (6003) 472 (22 Oct 2010) DOI: 10.1126/science.1186474

DDiviner Lunar Radiometer Observations of the LCROSS Impact - PO Hayne et al

• Science 330 (6003) 477 (22 Oct 2010) DOI: 10.1126/science.1197135

Diviner Lunar Radiometer Observations of Cold Traps in the Moon’s South Polar Region - DA Paige et al

• Science 330 (6003) 479 (22 Oct 2010) DOI: 10.1126/science.1187726

Hydrogen Mapping of the Lunar South Pole Using the LRO Neutron Detector Experiment LEND - IG Mitrofanov et al

• Science 330 (6003) 483 (22 Oct 2010) DOI: 10.1126/science.1185696

[makc]

...if there's less than 1% water you end up spending more energy than you generate by attempting to extract it...

what?

[neufer]

...if there's less than 1% water you end up spending more energy than you generate by attempting to extract it...

what?