Ski Luna!

Right now I'm enduring winter in snow-encrusted Boston, but my head is in The Woodlands, Texas, where more than 1,200 researchers have gathered for the annual Lunar and Planetary Science Conference. The LPSC is always a 'best bet" for hearing new discoveries about the solar system, and yesterday got off with a bang as scientists discussed water ice on the Moon — not whether it's there, but how much of it might be lying around.

Faint plume from LCROSS imact
Extensive image processing of images taken by the LCROSS shepherding spacecraft 15 seconds after the Centaur rocket's demise reveals a dim debris plume (6 to 8 km across) in the shadowed part of Cabeus crater.
NASA

I think 2009 will be remembered as the year we finally convinced ourselves that water is present on the Moon. Planetary scientists have speculated about its existence there for decades, because some craters at the lunar poles never, ever see sunlight and thus might serve as "cold traps" where ice (arriving on comets, presumably) could remain stable. But last year three lunar spacecraft returned results that have made the case for lunar ice all but certain.

The most dramatic findings came after NASA "bombed" the polar crater Cabeus last October 9th with its Lunar Crater Observation and Sensing Satellite (LCROSS) — though it took mission scientists a while to certify that the impact had dredged up water from the crater's shadowed floor.

It turns out there's more to this story: Yesterday NASA-Ames scientist Anthony Colaprete announced that, in addition to water, LCROSS had unearthed a whole kettle of volatile compounds in the plume of impact debris that rose from Cabeus. So far the tally includes sulfur dioxide (SO2), methanol (CH3OH), and the curious organic molecule diacetylene (H2C4).

Supercold lunar craters

Daytime temperatures near the Moon's north pole are dramatically colder than elsewhere, plunging to as low as 40K (–390°F) inside some craters. Those permanently shadows recesses, researchers now say, could harbor thick deposits of water ice.

Last year scientists also realized that whiffs of water cling to much of the lunar surface. An instrument built by American scientists but carried on India's Chandrayaan 1 spacecraft found the spectroscopic signature of water and hydroxyl (OH) ions over much of the Moon. Carlé Pieters, the Brown University researcher whose team designed the Moon Mineralogy Mapper (M3), had fortuitously extended its near-infrared coverage enough to record 2.8 and 3.0 microns, where the OH and water molecules have telltale absorptions.

Yesterday another Chandrayaan 1 instrument made a splash at LPSC, so to speak. Paul Spudis (Lunar and Planetary Institute) announced that NASA's Mini-SAR instrument had found evidence for water ice in more more than 40 small craters near the Moon's north pole. (Any water ice is not going anywhere soon — the Diviner instrument aboard NASA's Lunar Reconnaissance Orbiter finds that the interiors of these craters are the coldest locations ever measured in the solar system.)

The craters range in size from 1 to 9 miles (2 to 15 km), and according to a NASA press release the lunar stash could total up to 600 million tons of ice, depending on its thickness within each crater.

Radar map of Moon's north pole

In this radar map of the Moon's north pole, polarization of the reflected echoes shows scientists which craters are fresh (red circles) and which ones likely contain deposits of water ice (green circles). The ice is stable because the craters' interiors are permanently shadowed and never see sunlight. Click for a larger version.
P. Spudis / Geophys. Research Letters

Utilizing a compact synthetic aperture radar, Mini-SAR detects changes in the polarization of radio waves reflected off the lunar surface. Water ice is transparent to radio energy and causes the radar pulses to be scattered multiple times, creating a distinctive polarization echo. Spudis thinks the deposits inside some polar craters could be nearly pure ice.

If he's right, think of the potential for lunar tourism! Imagine a cozy chalet perched atop the rim of a lunar crater, basking in a perpetual lunar sunset and with the resplendent Earth periodically bobbing into view from behind a distant peak. Then you jump into your super-insulated space suit, slap on some sticks, and schuss straight down the inner rim until you bottom out.

But watch out for those lunar moguls — in space, no one can hear you "screaming starfish."

7 thoughts on “Ski Luna!

  1. coolstar

    The ice mentioned above, 600 million tons, works out to about 0.5 cubic kilometers of water. That’s really not very much. IF this study is correct, as it’s yet to be corroborated, it’s not enough water, AND it’s so hard to get to, that it shouldn’t influence human plans for a return to the moon AT ALL.

  2. Lin4dGary Linford

    I presume that the lunar north pole photograph featuring a prominent “south pole” arrow was simply a typographical error? For Coolstar to assert that c. 6×1011 kg of H2O “is not enough water” suggests this critic imagines obsolete chemical rocket fuel applications. I don’t agree. The Moon is not destined to become merely a cosmic “gas station” for passing stone age chemical rockets piloted by Buck Rogers, Space Cadet. In the 21st Century onward, helium-3 fueled fusion power plants on the Moon will facilitate the use of rail gun, magnetic levitation, and electrostatic propulsion methods to make this planet the primary space port in the Solar System. I would imagine 5×1011 kg of H2O should do quite nicely @ 600 kg/person to support a population of 109 people living inside airtight lunar cities.

  3. Anthony BarreiroAnthony Barreiro

    Whether or not there is water on the moon, how much, and in what form(s) are all interesting empirical questions. But it’s quite a leap from the possibility of water to visions of lunar cities and He3 spaceports.

    I’m curious if there have been any statistically valid surveys of the amateur astronomy community investigating attitudes toward human space flight. Am I in the minority among skygazers in believing that we urgently need to learn how to live sustainably on this planet, and that fantasies of moon colonies and rockets to the stars are a dangerous delusion? We’re already in the middle of space, with an excellent view of the cosmos on every dark clear night. What we can’t see from earth we can see with space telescopes and other robotic missions.

  4. Anthony BarreiroAnthony Barreiro

    Whether or not there is water on the moon, how much, and in what form(s) are all interesting empirical questions. But it’s quite a leap from the possibility of water to visions of lunar cities and He3 spaceports.

    I’m curious if there have been any statistically valid surveys of the amateur astronomy community investigating attitudes toward human space flight. Am I in the minority among skygazers in believing that we urgently need to learn how to live sustainably on this planet, and that fantasies of moon colonies and rockets to the stars are a dangerous delusion? We’re already in the middle of space, with an excellent view of the cosmos on every dark clear night. What we can’t see from earth we can see with space telescopes and other robotic missions.

  5. coolstar

    Here’s a nice article putting together the idiocies of He-3 mining on the moon: http://depletedcranium.com/helium-3-from-the-moon-dumbest-idea-ever/
    Water is reasonably abundant in the inner solar system in NEOs: given the small delta-V needed to reach them, they make MUCH MUCH better refueling stations than the moon.
    First elementary rule of spaceflight: don’t leave one deep gravity well to immediately plot down in another one.
    If you really, truly want to go back to the moon and have the TRILLIONS of dollars it would take to set up a permanently manned base (where most of the occupants have to spend 98% of their time hiding from cosmic rays and CME’s) then Alan Stern probably has come of with the cheapest source of water: deliver giant frozen baggies from earth. Note I didn’t say CHEAP I said CHEAPEST. (NEOs would be cheaper of course, but once you’ve refueled there, any sane person would want to go someplace more interesting than the moon).
    How did I get $trillions? ISS has cost well over $100 billion U.S. and setting up the infrastructure for permanently manned bases on the moon will be at least 10’s of times more expensive.
    For all the Lunies out there, don’t let a little science and basic arithmetic get in the way out of your dreams. All you need to do is figure out a way to make a profit while fulfilling those dreams……..

  6. Harry Betz

    Imagine a pie graph representing the U. S. Federal Anuual Budget. The amount spent for NASA and human as well as nonhuman space exploration is an extremely miniscule slice compared to Welfare, Defense, etc. Ceasing human lunar and planetary exploration will have virtuallu no effect on how much we spend (and waste) in other areas.

  7. Harry Betz

    Imagine a pie graph representing the U. S. Federal Anuual Budget. The amount spent for NASA and human as well as nonhuman space exploration is an extremely miniscule slice compared to Welfare, Defense, etc. Ceasing human lunar and planetary exploration will have virtuallu no effect on how much we spend (and waste) in other areas.

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