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NASA Spacecraft Shows Diverse, Wet Environments on Ancient Mars

Written by thomas · Filed Under Aeronautics News 

July 17, 2008

thomas

WASHINGTON, July 16 /PRNewswire-USNewswire/ — Two studies based on
data from NASA’s Mars Reconnaissance Orbiter have revealed that the Red
Planet once hosted vast lakes, flowing rivers and a variety of other wet
environments that had the potential to support life.

One study, published in the July 17 issue of Nature, shows that vast
regions of the ancient highlands of Mars, which cover about half the
planet, contain clay minerals, which can form only in the presence of
water. Volcanic lavas buried the clay-rich regions during subsequent, drier
periods of the planet’s history, but impact craters later exposed them at
thousands of locations across Mars. The data for the study derives from
images taken by the Compact Reconnaissance Imaging Spectrometer for Mars,
or CRISM, and other instruments on the orbiter.

“The big surprise from these new results is how pervasive and
long-lasting Mars’ water was, and how diverse the wet environments were,”
said Scott Murchie, CRISM principal investigator at the Johns Hopkins
University Applied Physics Laboratory in Laurel, Md.

The clay-like minerals, called phyllosilicates, preserve a record of
the interaction of water with rocks dating back to what is called the
Noachian period of Mars’ history, approximately 4.6 billion to 3.8 billion
years ago. This period corresponds to the earliest years of the solar
system, when Earth, the moon and Mars sustained a cosmic bombardment by
comets and asteroids. Rocks of this age have largely been destroyed on
Earth by plate tectonics. They are preserved on the moon, but were never
exposed to liquid water. The phyllosilicate-containing rocks on Mars
preserve a unique record of liquid water environments possibly suitable for
life in the early solar system.

“The minerals present in Mars’ ancient crust show a variety of wet
environments,” said John Mustard, a member of the CRISM team from Brown
University, and lead author of the Nature study. “In most locations the
rocks are lightly altered by liquid water, but in a few locations they have
been so altered that a great deal of water must have flushed though the
rocks and soil. This is really exciting because we’re finding dozens of
sites where future missions can land to understand if Mars was ever
habitable and if so, to look for signs of past life.”

Another study, published in the June 2 issue of Nature Geosciences,
finds that the wet conditions on Mars persisted for a long time. Thousands
to millions of years after the clays formed, a system of river channels
eroded them out of the highlands and concentrated them in a delta where the
river emptied into a crater lake slightly larger than California’s Lake
Tahoe, approximately 25 miles in diameter.

“The distribution of clays inside the ancient lakebed shows that
standing water must have persisted for thousands of years,” says Bethany
Ehlmann, another member of the CRISM team from Brown. Ehlmann is lead
author of the study of an ancient lake within a northern-Mars impact basin
called Jezero Crater. “Clays are wonderful at trapping and preserving
organic matter, so if life ever existed in this region, there’s a chance of
its chemistry being preserved in the delta.”

CRISM’s high spatial and spectral resolutions are better than any
previous spectrometer sent to Mars and reveal variations in the types and
composition of the phyllosilicate minerals. By combining data from CRISM
and the orbiter’s Context Imager and High Resolution Imaging Science
Experiment, the team identified three principal classes of water-related
minerals dating to the early Noachian period. The classes are
aluminum-phyllosilicates, hydrated silica or opal, and the more common and
widespread iron/magnesium-phyllosilicates. The variations in the minerals
suggest that different processes, or different types of watery
environments, created them.

“Our whole team is turning our findings into a list of sites where
future missions could land to look for organic chemistry and perhaps
determine whether life ever existed on Mars,” said Murchie.

NASA’s Jet Propulsion Laboratory in Pasadena, Calif., manages the Mars
Reconnaissance Orbiter mission for NASA’s Science Mission Directorate in
Washington. The Applied Physics Laboratory operates the CRISM instrument in
coordination with an international team of researchers from universities,
government and the private sector.

SOURCE NASA

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