November 14, 2009
A Rainbow on the Moon
An ice rainbow seen in cirrus clouds on Earth. (UCSB Dept. Geography)
Five weeks ago a crater from the LCROSS impact formed on the Moon. The pre-impact build-up had been sensational, but the actual event was largely invisible to observers on Earth. It was a different story on the Moon. The slowly growing impact ejecta curtain threw water ice particles and vapor far out into space. When the crater formed, flying ice particles could have refracted the glare of unfiltered sunlight into an “ice rainbow,” similar to those seen through very high altitude clouds on Earth. For a very brief time, a rainbow might have been visible to an observer standing on the lunar surface. And like its namesake, this rainbow is a promise – a promise that the Moon is habitable. It is an invitation to humanity to extend man’s domain to our nearest planetary neighbor.
The LCROSS science team’s initial analysis of ejected impact plume data found evidence for water. It appears that several other species, particularly some carbon substances also found in the cores of comets, may be present. The new results suggest that some lunar polar volatiles may have their origins from outside the Moon, deposited there over millions of years by the impact of comets and asteroids.
Over the last 50 years, the idea of water ice at the lunar poles has generated as much angst as excitement within the scientific community. Ice on the Moon was suggested by Watson, Murray and Brown in 1960. They recognized that, regardless of the fate of such substances elsewhere on the Moon, the dark, cold floors of polar craters might retain volatile substances. Rock and soil samples returned by the Apollo missions were not only bone-dry, but crystallized in a very reducing environment, suggesting that any indigenous lunar water, if present, must have been a very minor component. Apollo scientist Jim Arnold resurrected the Watson et al. hypothesis forty years ago, concluding that their original proposal of water ice at the poles was still feasible and that a polar lunar orbiter was needed to search for such deposits.
We know that over geologic time, the Moon was bombarded by water-bearing objects. Meteorites contain water, and just as they’ve landed on Earth, they’ve also hit the Moon. Moreover, we’ve detected water vapor in the tails of comets with Earth-based telescopes. But it was widely speculated that all this water must be lost from the Moon, which left the issue of polar ice unresolved.
Fifteen years ago, the 1994 Clementine orbiter mission revived our interest in the Moon’s polar regions. When Clementine’s images of the Moon’s poles revealed large areas of shadowed terrain, it reminded Gene Shoemaker and the science team of the Watson and Arnold papers. Large shadowed areas suggested that polar cold traps might really exist, so an experiment was improvised using the spacecraft transmitter to beam RF energy into the shadowed areas. Analysis of the radio echoes suggested the presence of ice in shadowed areas near the south pole. This result was questioned, largely because our team couldn’t repeat the passes using the improvised experiment.
In 1998, Lunar Prospector found evidence for excess hydrogen in the surface soils of both lunar poles. These data could not show what form the hydrogen was in and had very low spatial resolution. The issue, as to whether the observed polar hydrogen represented water ice in the dark cold traps or elemental hydrogen implanted by solar wind protons, was vigorously debated. The preponderance of evidence in the years since Lunar Prospector, suggests that water ice is present in the polar areas, but its form, distribution and physical state are completely unknown.
The current flotilla of lunar orbiting spacecraft carry several advanced sensors, all designed to better characterize the environment and deposits of the polar regions of the Moon. We have seen extremely low temperatures in the polar dark regions using the DIVINER instrument on the American Lunar Reconnaissance Orbiter (LRO) spacecraft. The Japanese Kaguya mission mapped the topography and terrain of the polar areas and showed us the extent of the shadowed areas. The Indian Chandryaan mission sent a probe into the south pole, mapped the extent of sunlight and carried two NASA instruments – the Moon Mineralogy Mapper (M3) and Mini-SAR radar. In September, the M3 instrument found significant amounts of water bound into mineral structures at high latitudes. The Mini-SAR instrument has made maps showing the interior of dark polar craters. These maps are being analyzed for scattering characteristics to determine whether water ice might be present there; our initial results will be announced soon.
Now, the LCROSS impactor – sent to kick up the dust of the polar dark regions – has shown us that water ice does exist there. We still don’t know how much water ice in total may be present; from Clementine, we estimated there are billions of metric tones of water ice present in the south polar area. Complete analysis of all of the remote sensing information in the next couple of years will ultimately give us a good estimate of the total amount of water available. Clementine also revealed peaks of near-permanent sunlight in proximity to regions of permanent darkness at the poles (where the sun’s circular rotation keeps temperatures benign).
If you don’t know where you’re going, any path will get you there.
The Moon has the resources needed to bootstrap a sustained, permanent human presence. It is the place where we can learn how to live and work productively in space. The Moon has put out a welcome mat. What are we waiting for?
17 Comments
RSS feed for comments on this post.
The web editors have closed comments for this blog.
“The Moon has put out a welcome mat. What are we waiting for?”
Frankly, some good reason for stepping on it. The welcome mat at my doorstep doesn’t cost anything to step on it. This one sure does.
A sustained human presence on the Moon is not something that is an established, or obviously connects with any, national priority. In fact, the last NASA Authorization bill specifically states that, in the short term, a lunar outpost will not have sustained human presence. That would have been a great place for Congress to look ahead to advocate sustained lunar presence someday. But they didn’t.
“If you don’t know where you’re going, any path will get you there.”
That seems to characterize this effort quite well!
In many respects, this is chasing the pot of gold at the end of your rainbow.
Comment by Herb Willhauser — November 14, 2009 @ 11:39 am
[...] says – John Matson/Scientific American The Moon Is Wet! – Richard A. Kerr/ScienceNOW Daily News A Rainbow on the Moon – Paul Spudis/Air & Space Magazine [...]
Pingback by Vacation on the Moon - Out of the Cradle — November 14, 2009 @ 1:45 pm
Paul Spudis,
You appreciation of the lunar ‘stuff’ had been very consistent and you have pushed my enthusiasm to a great desire to better understand the Moon. I am currently (re)reading your ‘Once and Future Moon’, Smithsonian Institution 1996, upon the exciting news on ‘water on the moon’ based on the LCROSS’s data.
Yes, indeed, the Moon is the “place where we can learn how to live and work productively in space’. In one article published on 9/14/09, ‘Objectives before Architecture’,you clearly articulated the main difficulty created by the ‘tyranny of the Rocket Equation’ and I do agree with the idea that our primary mission is to locate, access and process lunar resources in order to ‘learn how to use the lunar material and energy resources’; in order ‘to create the ability through the use of space resources to go anywhere and do everything’. We truely need to start designing missions that will attempt to understand the feasibility or the unfeasibility of such endeavor. That answers the question posed in this lunar water related article: “the Moon has put out a welcome mat. What are we waiting for?”
Comment by Ernst Wilson, Elizabeth City State University — November 14, 2009 @ 2:16 pm
some good reason for stepping on it.
Herb,
I’ve attempted to develop such a rationale here:
Objectives Before Architectures – Strategies Before Tactics
Going to the Moon to develop its resources will allow us to routinely access all of cislunar space. All of our space assets: commercial, national security, and (most) scientific satellites reside in this volume of space. Routine access to these satellites permits maintenance, expansion, and development of them. And this changes the rules of spaceflight.
Fundamentally, going back to the Moon to develop its resources changes everything. And in contrast to your statement, such was the intention of Vision for Space Exploration, authorized by two different Congresses in 2006 and 2008.
Comment by Paul D. Spudis — November 14, 2009 @ 3:40 pm
Ernst,
Nice to hear from you again. Thanks for your comments; I appreciate them. Glad you’re enjoying the book (again) — tell your students!
Comment by Paul D. Spudis — November 14, 2009 @ 3:43 pm
There is also wine?
Comment by lu — November 14, 2009 @ 4:36 pm
With the confirmation of bucketfuls of water and, it would seem, tasty hydrocarbons too! Ethanol?
Headline: “Scientists discover Moonshine!”
My main concern is over the nature of the Vision… post LCROSS. Will the unilateralist Vision of Bush/ ESAS/ Cx re-emerge to trounce the multi-lateralist Vision of Augustine? After all what’s at stake here: “Most Valuable Real Estate in the Solar System” (Peter Diamandis Huffington Post http://www.huffingtonpost.com/peter-diamandis/most-valuable-real-estate_b_357177.html )
Now where have I heard that before! Ahh Yes:
http://www.space.com/businesstechnology/technology/moon_next_020923-2.html
And they spelt Shackleton wrong!
I earnestly hope that you are correct and that not only are there 730,500 shuttle launches worth but a bountiful re-hydration cycle too. This space cadet reckons that revisiting the Moon Treaty may be the only way to preserve some of the science for future generations before it gets used to: “develop capabilities, plans, and options to ensure freedom of action in space, and, if directed, deny such freedom of action to adversaries.”
Time will tell!
Comment by brobof — November 14, 2009 @ 5:45 pm
brobof,
Well, we are talking about the most valuable piece of real estate in the Solar System, in the near field anyway. A good sales phrase has its own life!
In regard to preserving the scientific integrity of the ice deposits, there is more than enough lunar ice for that. We could take hundreds of core samples and archive them permanently to preserve that volatile record without any impact whatsoever to mining and extraction activities.
There’s plenty of water on the Moon for everybody. It’s role is to allow us to begin routine space operations and habitation. It doesn’t have to last us forever; by the time we get our foothold established there, we will have other opportunities and sources for volatiles, metals and energy.
Comment by Paul D. Spudis — November 15, 2009 @ 4:45 am
Amen to that!
“Lunar polar orbiters, using remote sensors to search for water-ice in the permanently shadowed frozen craters near the lunar poles. If ice is found, the Moon can become a refueling base not only for oxygen, which constitutes 86% by weight of rocket propellant and is already known to be the most abundant element on the lunar surface, but also for hydrogen, which is the remaining 14% by weight of rocket propellant. The first such mission, if started now, could be designed, built, flown and return information within five years, around 1995.”
Alternative Plan for U.S. National Space Program
Gerard K. O’Neill 1989 (For goodness sake!)
I remember well when Clementine (’94) Kudos! and later Lunar Prospector hinted at Lunar water reserves. Why do these things have to take sooo long?
Perhaps things will speed up a bit now!
Comment by brobof — November 15, 2009 @ 8:46 am
Hi Paul,
Of all the talk I have heard over the years on where we should go and what we should do in space, I want to tell you that your position – the exploitation of lunar
resources in support of human expansion into the solar system – seems the most rational, the most objective.
Given the near certainty in knowledge that water is there, do you think the moon will become the focus of NASA’s future human space flight program?
Comment by Philip Backman — November 15, 2009 @ 8:45 pm
Hi Phillip,
In a rational world, yes it would. But we don’t live in that world, so the Moon’s future is uncertain. NASA is wedded to the Apollo template of spaceflight (design, build, launch and abandon), so reusable vehicles, incremental steps and using space resources are alien concepts to them. It remains to be seen whether they can change the way they approach their business.
Thanks for your encouraging comments!
Comment by Paul D. Spudis — November 16, 2009 @ 4:40 am
Paul Spudis,
I will not be surprised to see a NASA shift of paradigm, based upon the new lunar dis(un)coveries, as I will nor be surprised to see astrolawyers revisit the 1979 Moon Agreement in order to come up with a new legal regime governing the principles of lunar activities.
regards,
ernst
Comment by Ernst Wilson, Elizabeth City State University — November 16, 2009 @ 2:05 pm
Paul,
I want to share a quote and an observation.
“We have to learn again that science without contact with experiments is an enterprise which is likely to go completely astray into imaginary conjecture.” — Hannes Alfven
With LCROSS, NASA kept contact with an experiment and took a calculated risk with a relatively small investment. The question is “WHEN will that investment pay off by affecting space exploration decisions.”
Thanks for stimulating these discussions!
Comment by Steve at NASA — November 16, 2009 @ 9:49 pm
Wondering is there a mineral that we can gain from probing the moon.
Comment by Spence — November 18, 2009 @ 6:57 pm
Spence,
There are a variety of minerals that make up the Moon’s crust. Almost all of them are common species that have no economic value on the Earth. The real value of lunar materials is their use in space. Extracting what’s needed and can be used from the Moon enables us to live and work in space easier and more cheaply. This is what makes lunar resources extremely valuable.
Comment by Paul D. Spudis — November 19, 2009 @ 4:44 am
[...] recent discussions about using lunar polar ice, some expressed concern that we would too rapidly devour what they perceive to be a limited [...]
Pingback by Thanksgiving on the Moon: A Lunar Feast | The Once and Future Moon — November 22, 2009 @ 3:47 pm
With all due respect to the academic community, profit is what will stimulate the effort to have a permanent human presence on the lunar surface. An affordable method to transport vacationers to a lunar resort would get the job done. From there. Timeshare condos, Lunar ski slopes, low g roller coasters, funds will pour in!
Comment by Plano Texas — September 3, 2010 @ 6:14 pm