NASA Spacecraft Shows Diverse, Wet Enviroments on Ancient Mars

Dwayne Brown
Headquarters, Washington
202-358-1726
[email protected]

Guy Webster
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-5011
[email protected]

Jennifer Huergo
The Johns Hopkins University Applied Physics Laboratory, Laurel, Md.
240- 228-5618
[email protected]

RELEASE: 08-177

NASA SPACECRAFT SHOWS DIVERSE, WET ENVIRONMENTS ON ANCIENT MARS

WASHINGTON -- 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.

For more information on the new studies, visit:

www.nasa.gov...


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