NASA Spacecraft Sees Ice on Mars Exposed by Meteor Impacts

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PASADENA, Calif. -- NASA's Mars Reconnaissance Orbiter has revealed
frozen water hiding just below the surface of mid-latitude Mars. The
spacecraft's observations were obtained from orbit after meteorites
excavated fresh craters on the Red Planet.

Scientists controlling instruments on the orbiter found bright ice
exposed at five Martian sites with new craters that range in depth
from approximately 1.5 feet to 8 feet. The craters did not exist in
earlier images of the same sites. Some of the craters show a thin
layer of bright ice atop darker underlying material. The bright
patches darkened in the weeks following initial observations, as the
freshly exposed ice vaporized into the thin Martian atmosphere. One
of the new craters had a bright patch of material large enough for
one of the orbiter's instruments to confirm it is water ice.

The finds indicate water ice occurs beneath Mars' surface halfway
between the north pole and the equator, a lower latitude than
expected in the Martian climate.

"This ice is a relic of a more humid climate from perhaps just several
thousand years ago," said Shane Byrne of the University of Arizona.

Byrne is a member of the team operating the orbiter's High Resolution
Imaging Science Experiment, or HiRISE camera, which captured the
unprecedented images. Byrne and 17 co-authors report the findings in
the Sept. 25 edition of the journal Science.

"We now know we can use new impact sites as probes to look for ice in
the shallow subsurface," said Megan Kennedy of Malin Space Science
Systems in San Diego, a co-author of the paper and member of the team
operating the orbiter's Context Camera.

During a typical week, the Context Camera returns more than 200 images
of Mars that cover a total area greater than California. The camera
team examines each image, sometimes finding dark spots that fresh,
small craters make in terrain covered with dust. Checking earlier
photos of the same areas can confirm a feature is new. The team has
found more than 100 fresh impact sites, mostly closer to the equator
than the ones that revealed ice.

An image from the camera on Aug. 10, 2008, showed apparent cratering
that occurred after an image of the same ground was taken 67 days
earlier. The opportunity to study such a fresh impact site prompted a
look by the orbiter's higher resolution camera on Sept. 12, 2009,
confirming a cluster of small craters.

"Something unusual jumped out," Byrne said. "We observed bright
material at the bottoms of the craters with a very distinct color. It
looked a lot like ice."

The bright material at that site did not cover enough area for a
spectrometer instrument on the orbiter to determine its composition.
However, a Sept. 18, 2008, image of a different mid-latitude site
showed a crater that had not existed eight months earlier. This
crater had a larger area of bright material.

"We were excited about it, so we did a quick-turnaround observation,"
said co-author Kim Seelos of Johns Hopkins University Applied Physics
Laboratory in Laurel, Md., "Everyone thought it was water ice, but it
was important to get the spectrum for confirmation."

The Mars orbiter is designed to facilitate coordination and quick
response by the science teams, making it possible to detect and
understand rapidly changing features. The ice exposed by fresh
impacts suggests that NASA's Viking 2 lander, digging into
mid-latitude Mars in 1976, might have struck ice if it had dug four
inches deeper.

The Viking 2 mission, which consisted of an orbiter and a lander,
launched in September 1975 and became one of the first two space
probes to land successfully on the Martian surface. The Viking 1 and
2 landers characterized the structure and composition of the
atmosphere and surface. They also conducted on-the-spot biological
tests for life on another planet.

NASA's Jet Propulsion Laboratory in Pasadena manages the Mars
Reconnaissance Orbiter for NASA's Science Mission Directorate in
Washington. Lockheed Martin Space Systems in Denver built the
spacecraft. The Context Camera was built and is operated by Malin.
The University of Arizona operates the HiRISE camera, which Ball
Aerospace & Technologies Corp., in Boulder, Colo., built. The Johns
Hopkins University Applied Physics Laboratory led the effort to build
the Compact Reconnaissance Imaging Spectrometer and operates it in
coordination with an international team of researchers.

To view images of the craters and learn more about the Mars
Reconnaissance Orbiter, visit:

http://www.nasa.gov/mro