Mars Orbiter Examines 'Lace' and 'Lizard Skin' Terrain

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Guy Webster 818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif.
guy.webster@jpl.nasa.gov

NEWS RELEASE: 2007-146 Dec. 11, 2007

Mars Orbiter Examines 'Lace' and 'Lizard Skin' Terrain

SAN FRANCISCO - Scrutiny by NASA's newest Mars orbiter is helping scientists learn the
stories of some of the weirdest landscapes on Mars, as well as more familiar-looking parts of the
Red Planet.

One type of landscape near Mars' south pole is called "cryptic terrain" because it once defied
explanation, but new observations bolster and refine recent interpretations of how springtime
outbursts of carbon-dioxide gas there sculpt intricate patterns and paint seasonal splotches.

"A lot of Mars looks like Utah, but this is an area that looks nothing like Planet Earth," said
Candice Hansen of NASA's Jet Propulsion Laboratory, Pasadena, Calif., deputy principal
investigator for the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's
Mars Reconnaissance Orbiter.

In addition to radially branching patterns called "spiders," which had been detected by an earlier
Mars orbiter, other intriguing ground textures in the area appear in the new images. "In some
places, the channels form patterns more like lace. In others, the texture is reminiscent of lizard
skin," Hansen said.

Results from all six instruments on the Mars Reconnaissance Orbiter, which reached Mars last
year, are described in dozens of presentations this week by planetary scientists in San Francisco
at the fall meeting of the American Geophysical Union.

By taking stereo pictures of a target area from slightly different angles during different orbits,
HiRISE can show the surface in three dimensions. Channels found to widen as they run uphill in
the cryptic terrain region testify that the channels are cut by a gas, not a liquid.

Earlier evidence for jets of gas active in the region came from fan-shaped blotches appearing
seasonally, which scientists interpret as material fallen to the surface downwind of vents where
the gas escapes. Some of the fans are dark, others bright. "The dark fans are probably dust, but
the exact composition of the brighter fans had remained unknown until now," said Tim Titus of
the U.S. Geological Survey's Astrogeology Team, Flagstaff, Ariz.

Observations by the new orbiter's Compact Reconnaissance Imaging Spectrometer for Mars
suggest that the bright fans are composed of carbon-dioxide frost. Here's the story researchers
now propose: Spring warms the ground under a winter-formed coating of carbon dioxide ice.
Thawing at the base of the coating generates carbon-dioxide gas, which carves channels as it
pushes its way under the ice to a weak spot where it bursts free. The jet of escaping gas carries
dust aloft and also cools so fast from expanding rapidly that a fraction of the carbon dioxide
refreezes and falls back to the surface as frost.

The processes creating the cryptic terrain are current events on Mars. Repeated HiRISE
observations of the same target area show the downwind fans can form and grow perceptibly in
less than five days.

Other new findings from the Mars Reconnaissance Orbiter reveal processes of Martian
environments long ago. A team including Chris Okubo of the University of Arizona, Tucson,
used stereo HiRISE images to examine layered deposits inside Mars' Candor Chasma, part of
Valles Marineris, the largest canyon system in the solar system.

"The high-resolution structural map allowed us to interpret the geological history of the area,"
Okubo said. "The layers are tilted in a way that tells us they are younger than the canyon."
Spectrometer studies of the composition of these deposits had indicated water played a role in
their formation, but their age relative to the formation of the canyon had been uncertain. The new
findings suggest water was present after the canyon formed.

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars
Reconnaissance Orbiter mission for the NASA Science Mission Directorate, Washington.
Lockheed Martin Space Systems, Denver, is the prime contractor for the project and built the
spacecraft. The University of Arizona operates the HiRISE camera, which was built by Ball
Aerospace and Technology Corp., Boulder, Colo. The Compact Reconnaissance Imaging
Spectrometer for Mars team, led by Johns Hopkins University's Applied Physics Laboratory,
includes expertise from universities, government agencies and small businesses in the United
States and abroad.

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