Thursday, November 14, 2013

Investigating the origin and location of the Moon's water

Map of energetic neutron absorption centered on the lunar South Pole on the rim of Shackleton crater and prepared by NASA (GSFC) using neutron absorption data collected by the Russian LEND experiment aboard LRO. The map shows areas where water ice is most likely to be become slowly trapped over aeons, areas of low solar incidence as well as places in permanent and near-permanent shadow.  Interestingly, not all the Moon's permanently shadowed regions (PSR's) show such an indication of volatile hydrogen while large areas receiving at least some sunlight apparently do. Note also the Moon's strongest signature at Cabeus, the LCROSS mission impact target in 2009. [NASA/GSFC/SVS/Roscosmos].
University of Alabama at Huntsville - One of the things Dr. Richard Miller thinks is coolest about working as part of a team investigating the origin and mapping of water on the lunar poles is that he can look up at night or when the Moon rises during the day and see the object of his research.

Making a visual connection with his subject is usually not an option for the professor at The University of Alabama in Huntsville (UAH), who specializes in high-energy astrophysics. Now, after having been part of the discovery of surface water at Shackleton Crater at the Moon's south pole, Dr. Miller finds himself on a team investigating questions that have been raised by that discovery.

"I remember as a little kid watching the Apollo missions to the Moon and the lunar landings," he said. "As a little kid, I watched and daydreamed about this, and then through a series of almost random events in life to find myself working as a part of the team on this is really pretty awesome."

Dr. Miller is associated with the work being done on lunar mapping by the Johns Hopkins University Applied Physics Lab, which leads the Volatiles, Regolith and Thermal Investigations Consortium for Exploration and Science (VORTICES) as part of NASA's Solar System Exploration Research Virtual Institute (SSERVI).

Dr. Richard Miller is leading a team applying new
data analysis techniques to improve understanding of
the nature of volatile hydrogen near the lunar poles
and map its distribution
[Michael Mercier/UAH].
"SSERVI is a NASA virtual research institute," said Dr. Miller, "composed of nine lead research teams from seven states based and managed at NASA's Ames Research Center in California," formally NASA's Lunar Sciences Institute.

VORTICES brings together scientific expertise across a broad range of disciplines. In addition to UAH, other collaborating institutions include NASA Goddard Space Flight Center, JPL, the Georgia Institute of Technology, the Lunar and Planetary Institute, Mount Holyoke College, Johns Hopkins University, the University of Alaska, University of Hawaii and University of Maine.

The five-year effort is focused on a deeper understanding of regolith, or soil, and volatiles - including water and hydroxide - on planetary bodies like the Moon, asteroids and other 'airless bodies' in the solar system.

"My particular component of the effort builds upon the previous work I've done identifying lunar water resources at the Moon's poles, including the first detection of lunar surface water within Shackleton Crater," Dr.Miller said. "I have received great support and encouragement from the entire Johns Hopkins team."

Some scientists think Shackleton's formations make a unique place for water collection from elsewhere, with high peaks around the rim that are exposed to near continual sunlight to invite volatile molecules and a deep and cold floor shrouded in darkness to hold and freeze them so they can't escape.

The crater lies very close to the moon's south pole and is approximately 20 kilometers in diameter and over 4 kilometers deep with steep sloping. Scientists are curious about whether Shackleton is truly special and unique in its endowment of surface water or if other craters may also hold volatiles.

Dr. Miller is leading a team effort to apply new techniques to data analyses from the past and to new data being collected currently, in order to better characterize the hydrogen at the lunar poles and map its spatial distribution. Hydrogen is a marker for water, though it can also be a marker for hydrogen compounds, like hydroxyl (OH). Both compounds, thought to originate from neutral hydrogen in the solar wind, have also been detected in full sunlight, close to the Moon's equator.

"That's what's exciting about this surface deposit at Shackleton Crater," said Dr. Miller. "It suggests there may be an easier way to get the material out" than to mine for it at depths of 1 meter or more, where other lunar water deposits have been found to reside.

"If you look at the water at the rest of the lunar poles, what makes this crater special? Is this really the only region that has water at the surface?" Dr. Miller asks.

Craters in permanent darkness rest between the rim of the enormous South Pole-Aitken basin and Shackleton crater. Now mapped in detail from LRO, local conditions or 'events' have led to an apparent build-up of frosts on parts of the floor of Shoemaker but far less on the floor of Haworth. LRO LOLA LDEM (40 meter per pixel resolution) [NASA/GSFC/LOLA Science Team].
Scientists are trying to understand how the water discovered so close to the surface at Shackleton Crater got there. Did it fly in on a comet or an asteroid? Could it have migrated there as part of a lunar water cycle? Or is there some other mechanism or combination of mechanisms involved?

"If most of the water broadly distributed across the lunar poles is buried, then what that says is that it may have been deposited episodically rather than continuously. Migration to the permanently shadowed regions at the poles from other areas of the moon may also play a role. Those craters at the lunar poles are so cold that once the water molecule dives into those craters, it freezes and doesn't leave," Dr. Miller said.

"We need to do more research to find out. Now we've moved beyond simple detection to ask, what is the lunar water cycle? We're bringing together all these data sets to determine what is going on at the poles of the Moon."

The detection and discovery of water on the Moon evolved in parallel with numerous other discoveries of water or hydrogen throughout the solar system, altering science's understanding and posing new questions: How and where do volatiles form in the solar system and how are they transported? How do they interact physically and chemically on solar system bodies? What are the formation and evolution processes for regoliths throughout the solar system? These are just some of the topics to be addressed by the VORTICES effort.

VORTICES will fill important knowledge gaps that will ultimately enable additional human exploration of the Moon, asteroids and elsewhere, identification of resources and a deeper scientific understanding of Earth's nearest cosmic neighbors. Lunar mapping work will include the abundance of water and some information on its depth distribution.

"My piece builds on the work my colleagues and I have done previously," Dr. Miller said. "I will be leveraging those discoveries to expand our understanding of the lunar water cycle, including the abundance, spatial and depth distributions of lunar hydrogen. The new detection and mapping techniques developed here will be extended to include new information such as elemental abundances via nuclear gamma-ray techniques, as well as topographical, temperature and albedo - optical, IR and UV reflection - measurements."

The analysis techniques and processes developed by the over 30 researchers on the VORTICES teams can be applied to water mapping on asteroids, other moons and planets. Work being done by all the SSERVI teams could also point scientists in new directions.

"All of the nine SSERVI teams selected are multi-institutional scientific collaborations," said Dr. Miller. "The work we do, or other teams do, may ultimately inform future space missions."

Related Posts:
GSFC releases LEND lunar water demonstration (June 3, 2013)
The Mystery of Shackleton Crater (April 8, 2013)
Water found in the Apollo 15 'Genesis Rock' (February 19, 2013)
Reflecting on the ice of Mercury and the Moon (December 3, 2012)
Water from the Sun (October 17, 2012)
Mini-RF adds to evidence of ice on Shackleton walls (September 1, 2012)
'A Resolve to Mine the Moon' (July 15, 2012)
Shackleton harbors ice, after all (June 12, 2012)
Who discovered water on the Moon? (June 1, 2012)
LRO LEND: "A Scientific Dispute" (March 27, 2012)
Shackleton on a Summer's Day (March 26, 2012)
Cosmic ray flux effects lunar ice (March 19, 2012)
Will LRO LEND prove effective? (February 21, 2012)
Shadowed fluffy lunar frost detected in starlight (January 14, 2012)
The Moon's metallic water (February 27, 2011)
Where are the wettest places on the Moon (October 23, 2010)
DLRE observes Moon's polar cold traps (October 26, 2010)
LRO analysis of LCROSS impact proves essential (October 21, 2010)
LRO DLRE (Diviner): Widespread Water on the Moon (October 21, 2010)
Shackleton: Out of the Shadows (September 17, 2009)

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