Wah....
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http://www.sciencedaily.com/releases/2011/11/
111102145736.htm
Did Life Once Exist Below Red Planet's Surface? NASA Study of Clays Suggests
Watery Mars Underground
enlarge
Impact cratering and erosion combine to reveal the composition of the Martian
underground by exposing materials from the subsurface. (Credit:
NASA/JPL-Caltech/JHUAPL)
ScienceDaily (Nov. 2, 2011) A new NASA study suggests if life ever existed on
Mars, the longest lasting habitats were most likely below the Red Planet's
surface.
A new interpretation of years of mineral-mapping data, from more than 350 sites
on Mars examined by European and NASA orbiters, suggests Martian environments
with abundant liquid water on the surface existed only during short episodes.
These episodes occurred toward the end of a period of hundreds of millions of
years during which warm water interacted with subsurface rocks. This has
implications about whether life existed on Mars and how the Martian atmosphere
has changed.
"The types of clay minerals that formed in the shallow subsurface are all over
Mars," said John Mustard, professor at Brown University in Providence, R.I.
Mustard is a co-author of the study in the journal Nature. "The types that
formed on the surface are found at very limited locations and are quite rare."
Discovery of clay minerals on Mars in 2005 indicated the planet once hosted
warm, wet conditions. If those conditions existed on the surface for a long
era, the planet would have needed a much thicker atmosphere than it has now to
keep the water from evaporating or freezing. Researchers have sought evidence
of processes that could cause a thick atmosphere to be lost over time.
This new study supports an alternative hypothesis that persistent warm water
was confined to the subsurface and many erosional features were carved during
brief periods when liquid water was stable at the surface.
"If surface habitats were short-term, that doesn't mean we should be glum about
prospects for life on Mars, but it says something about what type of
environment we might want to look in," said the report's lead author, Bethany
Ehlmann, assistant professor at the California Institute of Technology,
Pasadena, and scientist at NASA's Jet Propulsion Laboratory, also in Pasadena.
"The most stable Mars habitats over long durations appear to have been in the
subsurface. On Earth, underground geothermal environments have active
ecosystems."
The discovery of clay minerals by the OMEGA spectrometer on the European Space
Agency's Mars Express orbiter added to earlier evidence of liquid Martian
water. Clays form from the interaction of water with rock. Different types of
clay minerals result from different types of wet conditions.
During the past five years, researchers used OMEGA and NASA's Compact
Reconnaissance Imaging Spectrometer, or CRISM, instrument on the Mars
Reconnaissance Orbiter to identify clay minerals at thousands of locations on
Mars. Clay minerals that form where the ratio of water interacting with rock is
small generally retain the same chemical elements as those found in the
original volcanic rocks later altered by the water.
The study interprets this to be the case for most terrains on Mars with iron
and magnesium clays. In contrast, surface environments with higher ratios of
water to rock can alter rocks further. Soluble elements are carried off by
water, and different aluminum-rich clays form.
Another clue is detection of a mineral called prehnite. It forms at
temperatures above about 400 degrees Fahrenheit (about 200 degrees Celsius).
These temperatures are typical of underground hydrothermal environments rather
than surface waters.
"Our interpretation is a shift from thinking that the warm, wet environment was
mostly at the surface to thinking it was mostly in the subsurface, with limited
exceptions," said Scott Murchie of Johns Hopkins University Applied Physics
Laboratory in Laurel, Md., a co-author of the report and principal investigator
for CRISM.
One of the exceptions may be Gale Crater, the site targeted by NASA's Mars
Science Laboratory mission. Launching this year, the mission's Curiosity rover
will land and investigate layers that contain clay and sulfate minerals.
NASA's Mars Atmosphere and Volatile Evolution Mission, or MAVEN, in development
for a 2013 launch, may provide evidence for or against this new interpretation
of the Red Planet's environmental history. The report predicts MAVEN findings
consistent with the atmosphere not having been thick enough to provide warm,
wet surface conditions for a prolonged period.
JPL, a division of Caltech, manages the Mars Reconnaissance Orbiter for NASA's
Science Mission Directorate in Washington. APL provided and operates CRISM. For
more information about the Mars Reconnaissance Orbiter, visit:
http://www.nasa.gov/mro and http://mars.jpl.nasa.gov/mro .
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Story Source:
The above story is reprinted from materials provided by NASA/Jet Propulsion
Laboratory.
Note: Materials may be edited for content and length. For further
information, please contact the source cited above.
Journal Reference:
Bethany L. Ehlmann, John F. Mustard, Scott L. Murchie, Jean-Pierre Bibring,
Alain Meunier, Abigail A. Fraeman, Yves Langevin. Subsurface water and clay
mineral formation during the early history of Mars. Nature, 2011; 479 (7371):
53 DOI: 10.1038/nature10582
Need to cite this story in your essay, paper, or report? Use one of the
following formats:
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NASA/Jet Propulsion Laboratory (2011, November 2). Did life once exist below
Red Planet's surface? NASA study of clays suggests watery Mars underground.
ScienceDaily. Retrieved November 3, 2011, from http://www.sciencedaily.com
/releases/2011/11/111102145736.htm
Note: If no author is given, the source is cited instead.
Disclaimer: Views expressed in this article do not necessarily reflect those of
ScienceDaily or its staff.
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