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No Ice on the Moon
eldavojohn writes "In 1994, there was speculation that there might be a southern ice cap on the moon — something our exploration of it could take advantage of. Unfortunately, recent evidence has come to light revealing that this probably isn't true." From the article: "If there is any ice at the South Pole, it probably comes from tiny, scattered grains that probably account for only one or two percent of the local dust, the authors suggest. "Any planning for future exploitation of hydrogen at the Moon's South Pole should be constrained by this low average abundance rather than by the expectation of localized deposits at higher concentrations," the paper says soberly. The research involved sending a radar signal from the Arecibo telescope in Puerto Rico. The signal hit the southern lunar region and the reflection was picked up by the Green Bank Telescope in West Virginia." Well, it looks like we're going to have to hit Hoth before we hold that kegger on the moon."
I live in WV and have seen the Green Bank Telescope. Impressive radio telescope. Not as impressive as Arecibo though. I was expecting more like an array but it really is just one giant dish.
Better link than in the story:
http://www.gb.nrao.edu/
B.
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1% (speculated proportion of water in the dust) seems like a lot to me. Separating that 1% of water from the dust would probably be more cost effective than bringing it up from Earth.
We're whalers on the moon, We carry a harpoon. But there ain't no whales So we tell tall tales And sing our whaling tune.
Just send a bunch of scornful women to the moon, and there will be LOTS of ice in no time.
By that I mean, I hate my wife.
Science fiction writers (the hard- variety) like Stephen Baxter have been lamenting the likelyhood of this eventuality for years now. Not that it isn't nice to at least have some closure, but on the other hand it seems like the news is little more than the last nail in the coffin for the most obvious pas-de-terre between Earth and space.
There is one book--Manifold Space, I think it might be--that muses upon the notion that there may be some water deeply buried (e.g. 20+ kilometres) the surface, and all the difficulties involved in getting to it (e.g. standard mining techniques developed on Earth wouldn't work there for a host of reasons). Excellent book/series, incidentally. Strongly recommended for any space science enthusiasts.
Wasn't there also talk about ice in deep craters situated where the sun can never shine on it?
...at least that's what I recall. It sounds kinda plausible.
The theory was (and I hope I have this right) that cometary ice must impact the moon from time to time - so there is water there from time to time - but whenever the sun shines, in the absence of an atmosphere, the water will evaporate (sublimate?) away quite quickly during the lunar day - then freeze out of the atmosphere during the night.
This mechanism would generally keep whatever water molecules there is up there moving around...*UNTIL* (by chance) it lands somewhere where there is never any sunlight - inside a cave or a deep crater. At that point it must settle - and there is no longer a mechanism to move it around again. With no atmosphere to scatter sunlight, permenantly dark places will be profoundly cold.
It follows then that whatever water there is will always end up in these relatively rare places EVENTUALLY - so given enough time, all of the moon's water would end up stashed away in just a few easy-to-predict places.
Furthermore, we'd never be able to see those places from earth-bound or low orbit telescopes because any place we can see must also collect sunlight at some point in the lunar orbit.
www.sjbaker.org
The real question is what percent of that dust is cheese!?
Sometimes stories just go back, and not forth. I suspect this is one of them.
Back in the Apollo days, a Saturn V third stage was allowed to smash into the moon so seismographs could pick up the vibrations. This and other tests allowed scientists to get a basic idea of the moon's interior structure. A core or crust of ice would have been pretty obvious. If there was any ice, it would have to be just traces.
Our instruments are getting increasingly better. This is a case of a hypothesis based on observations by a crude instrument being disproved by follow-up investigations by more sophisticated gear.
I'm disappointed, but hey, the universe wasn't designed to things easy for us.
Gold is economical to extract from ore that has less than one ounce of gold per ton.
Water is going to be more valuable than gold to someone on the Moon.
Water is way easy to extract.
Mmm, actually, the way it worked is this:
(1) Clementine observed a particular wiggle in the radar reflection. At the time, it was thought the only reasonable way to get that wiggle was to have the radar reflect off ice. Huzzah! Ice! (Well, not really. It hasn't been directly observed -- no one's held it in their hand -- but it seemed no other explanation would account for the wiggle.)
(2) Now someone has come up with an alternative explanation for the wiggle, and demonstrated that you can get it from areas (sunlit areas) which really shouldn't have ice. Throws cold water, so to speak, on the idea that only ice can make the radar signature wiggle.
But does this mean no ice? Nope. Now we have two explanations for Clementine's observation: ice or some surface roughness thingy. Which is the right cause? Could be ice, could be merely rough rocks, could be both.
So it's not that ice on the Moon has been disproved. It's that a previous proof (or strong suggestion of) ice on the Moon has been shown to be in error. Doesn't mean the ice isn't there. Just means we no longer know (or think we know) whether it is or not. Have to go take a shovel and find out, I think.
OK, whoever gave this a +1 Informative mod - hand over your Geek Card! You are no longer a card-carrying Geek. Please take a Dork card on your way out. (Geeks know that radio waves and light are two different ways to refer to the same thing, and that yes, it matters if you block it when you're talking about a telescope observing any part of the spectrum.)
If you mod me down, I shall become more powerful than you could possibly imagine.
This study does *not* indicate that there is no ice in permanently shadowed areas of the Moon. Before this study came out, there were two widely cited lines of evidence for ice:
1) Lunar Prospector found elevated hydrogen near the poles using a neutron spectrometer
2) Clementine bi-static radar (and later ground-based measurements) found backscatter effects that looked like ice
Most planetary geologists weighted (1) more heavily. There was always a lot of argument about interpretation of (2).
Now this study comes along and fairly definitively throws out (2) by showing the data has another explanation. Fine. From (1) we still have solid evidence of hydrogen near the poles, and most geologists would agree that the likeliest explanation of that hydrogen is water ice deposits in permanently dark crater interiors (the only places cold enough for ice to be stable in a vacuum).
So the main impact of this study is to suggest (but not prove) that ice, if present, is not found in clumps of centimeter scale or larger. And the 1% concentration figure they cite is a *lower* bound, not an upper bound. That is, ice could be more concentrated than 1% in some regions below neutron spectrometer resolution (e.g. kilometer scale) and we would have no way to know.