[meteorite-list] MRO Spacecraft Shows Diverse, Wet Environments on Ancient Mars

[Ron Baalke]

July 16, 2008

Dwayne Brown 
Headquarters, Washington
202-358-1726
dwayne.c.brown at nasa.gov

Guy Webster 
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-5011
guy.webster at jpl.nasa.gov

Jennifer Huergo
The Johns Hopkins University Applied Physics Laboratory, Laurel, Md.
240- 228-5618
jennifer.Huergo at jhuapl.edu

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:

http://www.nasa.gov/mro

	
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