[meteorite-list] NASA Spacecraft Read Layered Clues to Changes on Mars

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed, 13 Dec 2006 10:45:43 -0800 (PST)
Message-ID: <200612131845.KAA15728_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/news.cfm?release=2006-148

NASA Spacecraft Read Layered Clues to Changes on Mars
Guy Webster, 818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif.

2006-148

December 13, 2006

SAN FRANCISCO -- Layers on Mars are yielding history lessons revealed by
instruments flying overhead and rolling across the surface.

Some of the first radar and imaging results from NASA's newest Mars
spacecraft, the Mars Reconnaissance Orbiter, show details in layers of
ice-rich deposits near the poles. Observed variations in the layers'
thickness and composition will yield information about recent climate
cycles on the red planet.

NASA's Mars Exploration Rover Opportunity has photographed patterns in
the layering of crater-wall cliffs that are the clearest evidence of
ancient sand dunes the rover has seen since arriving at Mars nearly
three years ago. The science team for Opportunity's twin, Spirit, is
using new orbital images of the rover's surroundings to interpret how
some rocks with minerals altered by water fit into the area's complex
layered structure.

"The combination of instruments on Mars Reconnaissance Orbiter is such a
great advantage," said Dr. Jack Mustard of Brown University, Providence,
R.I. He is deputy principal investigator for the Compact Reconnaissance
Imaging Spectrometer for Mars, a mineral-identifying instrument on Mars
Reconnaissance Orbiter. Researchers are using mineral information from
analyses of spectrometer observations, combined with images from the
orbiter's High Resolution Imaging Science Experiment, to seek the source
of the mineral gypsum in dunes near the Martian north pole and clay
minerals elsewhere. Gypsum and clay minerals are indicators of formerly
wet conditions.

Other new images from that camera show mysterious pitting in the layered
terrain near the north pole. Nearby, a steep slope exposing the layers
appears to be shedding blocks of icy material that disappear instead of
accumulating at the bottom of the slope.

"Observations of the polar layered deposits are telling us about the
material properties there," said Dr. Ken Herkenhoff of the U.S.
Geological Survey, Flagstaff, Ariz. "These deposits record relatively
recent climate variations on Mars, like recent ice ages on Earth."

The Shallow Subsurface Radar instrument on Mars Reconnaissance Orbiter
has begun probing through similar layered deposits at Mars' south pole.
"The radar is penetrating through the entire thickness of these deposits
and revealing the fine-scale internal layering," said Dr. Roger Phillips
of Washington University, St. Louis, the deputy team leader for that
instrument.

Far from the poles, Opportunity is navigating the scalloped rim of
Victoria crater about half a mile in diameter, stopping at promontories
along the way to look at cliff walls of adjacent promontories. The top
part of the stack of layers exposed in the cliffs appears to be rocky
rubble thrown outward by the impact that dug the crater. "We see an
abrupt transition between the jumbled-up material and intact layers
below it that are still in place from before the impact," said Dr. Steve
Squyres of Cornell University, Ithaca, N.Y., principal investigator for
the rovers. Some of the intact layering resembles fossilized dunes in
the U.S. Southwest.

Spirit recently found water-altered minerals in disturbed soils and
granular rocks near where the rover spent the Martian winter. An image
of the region from Mars Reconnaissance Orbiter is aiding interpretation
of how different parts of the terrain, such as a bright platform
nicknamed "Home Plate," are related to others. "It appears likely that
these rocks came from one or more volcanic explosions that produced
'Home Plate,'" said Dr. Ray Arvidson, also of Washington University,
deputy principal investigator for the rovers.

Dr. John Callas of NASA's Jet Propulsion Laboratory, Pasadena, Calif.,
project manager for the rovers, said, "The biggest news about the health
of the rovers is that it is essentially unchanged from nine months ago.
Each rover has operated more than 1,000 Martian days on the surface of
Mars. They are well past their original design life of 90 Martian days,
and there is always the possibility that a critical component on either
rover could stop functioning at any time, so we operate the rovers with
that in mind and value each additional day they continue to work."

Researchers are describing the latest findings of Mars Reconnaissance
Orbiter and the twin rovers today at the American Geophysical Union
meeting in San Francisco. New images from the orbiter and rovers can be
seen at: http://www.nasa.gov/mission_pages/MRO/news/mro-20061213.html .

JPL, a division of the California Institute of Technology, manages the
Mars Reconnaissance Orbiter and Mars Exploration Rover missions for the
NASA Science Mission Directorate, Washington. Lockheed Martin Space
Systems, Denver, is the prime contractor for the orbiter. The Johns
Hopkins University Applied Physics Laboratory, Laurel, Md., provided and
operates the Compact Reconnaissance Imaging Spectrometer. The High
Resolution Imaging Science Experiment is operated by the University of
Arizona, Tucson, and the instrument was built by Ball Aerospace and
Technology Corp., Boulder, Colo. The Shallow Subsurface Radar was
provided by the Italian Space Agency and its operations are led by the
INFOCOM Dept., University of Rome "La Sapienza."
Received on Wed 13 Dec 2006 01:45:43 PM PST