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September
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.
The
observations were made by NASA's Moon Mineralogy Mapper, or
M3 ("M-cubed"), aboard the Indian Space
Research Organization's Chandrayaan-1 spacecraft. NASA's Cassini
spacecraft and NASA's Epoxi spacecraft have confirmed the
find.
Above:
A very young lunar crater as viewed by NASA's Moon Mineralogy
Mapper. On the right, the distribution of water-rich minerals
is shown in false-color blue. [more]
"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. "When
we say 'water on the Moon,' we are not talking about lakes,
oceans or even puddles," explained Carle Pieters, M3's
principal investigator from Brown University, Providence,
R.I. "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.
Above:
Data from NASA's Moon Mineralogy Mapper. The image on the
left shows albedo, or the sunlight reflected from the surface
of the Moon. The image on the right shows where infrared light
is absorbed by water and hydroxyl molecules. The water signature
is strongest at cool, high latitudes near the poles. The blue
arrow indicates Goldschmidt crater, a large feldspar-rich
region with a higher water and hydroxyl signature. Image credit:
ISRO/NASA/JPL-Caltech/Brown Univ. [more]
"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."
The
discovery of water molecules and hydroxyl on the Moon raises
new questions about the origin of "Moon water" and
its effect on lunar mineralogy. Answers to these questions
will be studied and debated for years to come.
Click
here for more images and information related to this story.
Editor: Dr.
Tony Phillips | Credit: Science@NASA
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