September 25, 2009 (ENS) - A thin layer of surface dew appears to form on the surface of the Moon then dissipate each day, new data from spacecraft reveal.
Data from the Deep Impact spacecraft and also from the Moon Mineralogy Mapper, M3, an instrument aboard India's Chandrayaan-1 spacecraft, provide for the first time, clear evidence that water exists on the surface of the Moon, according to scientists with the National Aeronautics and Space Administration, NASA, the Indian Space Research Organizaion and University of Maryland.
NASA scientists said Thursday that instruments aboard three separate spacecraft revealed water molecules in amounts that are greater than predicted, but still relatively small. Hydroxyl, OH, a molecule consisting of one oxygen atom and one hydrogen atom, also was found in the lunar soil. The findings were published in Thursday's edition of the journal "Science."
"Water ice on the moon has been something of a holy grail for lunar scientists for a very long time," said Jim Green, director of the Planetary Science Division at NASA Headquarters in Washington. "This surprising finding has come about through the ingenuity, perseverance and international cooperation between NASA and the India Space Research Organization."
The scientists are not talking about a lot of water on the Moon.
Carle Pieters, M3's principal investigator from Brown University explained, "When we say 'water on the Moon,' we are not talking about lakes, oceans or even puddles. Water on the Moon means molecules of water and hydroxyl that interact with molecules of rock and dust specifically in the top millimeters of the moon's surface."
Water on the Moon shows up as blue in this image from NASA's Moon Mineralogy Mapper on the Chandrayaan-1 spacecraft. (Image by ISRO/NASA/JPL-Caltech/Brown/USGS)
"The Deep Impact observations of the Moon not only unequivocally confirm the presence of OH/H2O on the lunar surface, but also reveal that the entire lunar surface is hydrated during at least some portions of the lunar day," writes University of Maryland astronomer with the unlikely name of Jessica Sunshine, and her co-authors in a paper in Thursday's issue of "Science."
"Finding water on the Moon in daylight is a huge surprise, even if it is only a small amount of water and only in the form of molecules stuck to soil," said Sunshine, who also co-authored a companion "Science" paper based on data from the M3 instrument that first detected the presence of lunar water.
Prevailing scientific opinion long has been that there probably is no water on the Moon and that, even if it does exist, it would be only in permanently cold, shadowed craters at the lunar poles.
"In the Deep Impact data we're essentially watching water molecules form and then dissipate right in front of our eyes," said Sunshine, who said her first reaction to the Moon Mineralogy Mapper data was skepticism.
"We aren't certain yet how this happens," she said, "but our findings suggest a solar driven cycle in which layers of water only a few molecules thick form, dissipate and reform on the surface each lunar day."
"We postulate that hydrogen ions from the Sun are carried by the solar wind to the Moon and there interact with oxygen rich minerals in lunar soil to produce the water and hydroxyl molecules that spectral analysis unequivocally show us are there," she said.
"In a cycle that occurs entirely in daylight, this water is formed in the morning, substantially lost by lunar mid-day, and re-formed as the lunar surface cools towards evening," the astronomer said.
"If this is correct, then such hydration via solar wind would be expected to occur throughout the inner Solar System on all airless bodies with oxygen-bearing minerals on their surfaces," she said.
Co-author University of Maryland Astronomer Michael A'Hearn, the Deep Impact and EPOXI science team leader, said, "I think it is tremendous that the Deep Impact spacecraft, which was the first to detect ice on a cometary nucleus, has now demonstrated the existence of adsorbed water on the Moon."
"This great spacecraft and its instruments continue to make important, unexpected discoveries long after the prime mission has ended," he said.
Another reflection of the scientific significance of finding water on the moon was simply that it generated three papers in the current issue of Science and a NASA press conference.
In addition to the M3 and Deep Impact articles, a third "Science" paper presented evidence collected by NASA's Cassini spacecraft. Water molecules and hydroxyl previously were suspected in data from a Cassini flyby of the moon in 1999, but the findings were not published until now.
"The data from Cassini's VIMS instrument and M3 closely agree," said Roger Clark, a U.S. Geological Survey scientist in Denver and member of both the VIMS and M3 teams.
"We see both water and hydroxyl. While the abundances are not precisely known, as much as 1,000 water molecule parts-per-million could be in the lunar soil. To put that into perspective, if you harvested one ton of the top layer of the moon's surface, you could get as much as 32 ounces of water."
Copyright Environment News Service, ENS, 2009. All rights reserved.
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