Sept. 24, 2009: NASA scientists have discovered water molecules in the
polar regions of the moon. Instruments aboard three separate
spacecraft revealed water molecules in amounts that are greater than
predicted, but still relatively small. Hydroxyl, 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.
These images show a very young lunar crater on the side of the moon that faces away from Earth, as viewed by NASA's Moon Mineralogy Mapper on the Indian Space Research Organization's Chandrayaan-1 spacecraft. On the left is an image showing brightness at shorter infrared wavelengths. On the right, the distribution of water-rich minerals (light blue) is shown around a small crater. Both water- and hydroxyl-rich materials were found to be associated with material ejected from the crater. Credits: ISRO/NASA/JPL-Caltech/USGS/Brown Univ.
NASA's Moon Mineralogy Mapper, or M3, instrument reported the
observations. M3 was carried into space on Oct. 22, 2008, aboard the
Indian Space Research Organization's Chandrayaan-1 spacecraft. Data
from the Visual and Infrared Mapping Spectrometer, or VIMS, on NASA's
Cassini spacecraft and the High-Resolution Infrared Imaging
Spectrometer on NASA's EPOXI spacecraft contributed to confirmation
of the finding. The spacecraft imaging spectrometers made it possible
to map lunar water more effectively than ever before.
The confirmation of elevated water molecules and hydroxyl at these
concentrations in the moon's polar regions raises new questions about
its origin and effect on the mineralogy of the moon. Answers to these
questions will be studied and debated for years to come.
"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."
From its perch in lunar orbit, M3's state-of-the-art spectrometer
measured light reflecting off the moon's surface at infrared
wavelengths, splitting the spectral colors of the lunar surface into
small enough bits to reveal a new level of detail in surface
composition. When the M3 science team analyzed data from the
instrument, they found the wavelengths of light being absorbed were
consistent with the absorption patterns for water molecules and
hydroxyl.
"For silicate bodies, such features are typically attributed to water
and hydroxyl-bearing materials, " said Carle Pieters, M3's principal
investigator from Brown University. "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. "
The M3 team found water molecules and hydroxyl at diverse areas of the
sunlit region of the moon's surface, but the water signature appeared
stronger at the moon's higher latitudes. 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."
For additional confirmation, scientists turned to the EPOXI mission
while it was flying past the moon in June 2009 on its way to a
November 2010 encounter with comet Hartley 2. The spacecraft not only
confirmed the VIMS and M3 findings, but also expanded on them.
"With our extended spectral range and views over the north pole, we
were able to explore the distribution of both water and hydroxyl as a
function of temperature, latitude, composition, and time of day, "
said Jessica Sunshine of the University of Maryland. Sunshine is
EPOXI's deputy principal investigator and a scientist on the M3 team.
"Our analysis unequivocally confirms the presence of these molecules
on the moon's surface and reveals that the entire surface appears to
be hydrated during at least some portion of the lunar day."
NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the M3
instrument, Cassini mission and EPOXI spacecraft for NASA's Science
Mission Directorate in Washington. The Indian Space Research
Organization built, launched and operated the Chandrayaan-1
spacecraft.
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