[meteorite-list] Mars Odyssey's Temperature Maps Expose Rock Layer History

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:04:54 2004
Message-ID: <200205292111.OAA03105_at_zagami.jpl.nasa.gov>

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Mars Odyssey's Temperature Maps Expose Rock Layer History
May 29, 2002

There are tantalizing indications emerging from the
thousands of infrared images taken so far by NASA's
Mars Odyssey spacecraft that Mars experienced a series
of environmental changes during active geological periods
in its history.

"We knew from Mars Global Surveyor that Mars was
layered, but these data from Odyssey are the first direct
evidence that the physical properties of the layers are
different. It's evidence that the environment changed
over time as these layers were laid down," said Dr. Philip
Christensen, principal investigator for Odyssey's camera
system and professor at Arizona State University, Tempe.
"The history of Mars is staring us in the face in these
different layers, and we're still trying to figure it all
out."

"I expect that the primitive geologic maps of Mars
that we have constructed so far will all be redrawn based
on Odyssey's new information," said Dr. R. Stephen
Saunders, Odyssey's project scientist at NASA's Jet
Propulsion Laboratory, Pasadena, Calif.

A mosaic of daytime infrared images of the layered Terra
Meridiani region shows a complex geology with craters and
eroded surfaces, exposing at least four distinct layers of
rock. Though the image does not include the infrared "colors"
of the landscape (showing surface mineral composition), it
does map the temperatures of the features, with surprising
results.

"With these temperature data, Odyssey has already lived up
to our expectations, but Mars, in fact, has exceeded our
expectations," said Christensen. "It would have been entirely
possible for the rocks of Mars to have been very similar and
thus give us all the same temperatures, but Mars has a more
interesting story to tell and we have the data to tell it."

The images can be seen at:

http://www.jpl.nasa.gov/images/mars/index.html

      and

http://themis.asu.edu.

Christensen is presenting his findings today at the spring
meeting of the American Geophysical Union in Washington, D.C.

"When we look at these distinct layers we see that the
temperatures are very different, indicating that there are
significant differences in the physical properties of the
rock layers," Christensen said.

The differences in surface temperature could be caused by
the fundamental differences in either the size of the rock
fragments in the layer, the mineral composition or the density
of the layers.

Odyssey's imaging team is working on fully processing the
infrared images, a complex and difficult task. When finished,
the data will help them test some important theories about
what causes the layers on Mars by examining the mineral
composition of the specific layers.

Plausible explanations include a history of volcanic activity
depositing layers of lava and volcanic ash; a history of
different processes that created the layers through wind and
water; or a history of climate change that varied the nature
of the materials deposited.

Christensen theorizes that the layers are caused not by
surface effects, but by changes in the planet's subsurface
water table. The presence or absence of water and the minerals
carried in it can significantly affect how sediment particles
are cemented together. With no clear evidence for surface water,
precipitation or runoff, Christensen believes that changes
in levels of underground water percolating through layers of
buried sediments could account for differences in rock
composition between layers. More complete infrared data will
help to confirm or disprove this and many other hypotheses
concerning Mars' geology.

"Looking at craters, we're seeing new distributions of rock
on the surface that are helping us understand events in martian
geology, and we are getting our first glimpses of 'color'
infrared images, which will help us precisely determine the
composition of the Mars' surface. This is just the beginning,"
Christensen said.

Additional information about the 2001 Mars Odyssey is available
on the Internet at:

http://mars.jpl.nasa.gov/odyssey/.

JPL, a division of the California Institute of Technology in
Pasadena, manages the 2001 Mars Odyssey mission for NASA's
Office of Space Science in Washington, D.C. Investigators at
Arizona State University in Tempe, the University of Arizona in
Tucson and NASA's Johnson Space Center, Houston, operate the
science instruments. Additional science partners are located at
the Russian Aviation and Space Agency and at Los Alamos National
Laboratories, New Mexico. The thermal emission imaging system
was provided by Arizona State University in collaboration with
Raytheon Santa Barbara Remote Sensing. Lockheed Martin
Astronautics, Denver, is the prime contractor for the project,
and developed and built the orbiter. Mission operations are
conducted jointly from Lockheed Martin and from JPL.
Received on Wed 29 May 2002 05:11:56 PM PDT