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[http://www.jpl.nasa.gov](http://www.jpl.nasa.gov/)

Guy Webster (818) 354-6278

Jet Propulsion Laboratory, Pasadena, Calif.

Dolores Beasley (202) 358-1753

NASA Headquarters, Washington

NEWS RELEASE: 2005-152 September 20, 2005

ORBITER\'S LONG LIFE HELPS SCIENTISTS TRACK CHANGES ON MARS

New gullies that did not exist in mid-2002 have appeared on a Martian
sand dune.

That\'s just one of the surprising discoveries that have resulted from
the extended life of NASA\'s Mars Global Surveyor, which this month
began its ninth year in orbit around Mars. Boulders tumbling down a
Martian slope left tracks that weren\'t there two years ago. New impact
craters formed since the 1970s suggest changes to age-estimating models.
And for three Mars summers in a row, deposits of frozen carbon dioxide
near Mars\' south pole have shrunk from the previous year\'s size,
suggesting a climate change in progress.

\"Our prime mission ended in early 2001, but many of the most important
findings have come since then, and even bigger ones might lie ahead,\"
said Tom Thorpe, project manager for Mars Global Surveyor at NASA\'s Jet
Propulsion Laboratory, Pasadena, Calif. The orbiter is healthy and may
be able to continue studying Mars for five to 10 more years, he said.

Mars years are nearly twice as long as Earth years. The orbiter\'s
longevity has enabled monitoring of year-to-year patterns on Mars, such
as seasonal dust storms and changes in the polar caps. \"Mars is an
active planet, and over a range of timescales changes occur, even in the
surface,\" said Dr. Michael Malin of Malin Space Science Systems, San
Diego, principal investigator for the Mars Orbiter Camera on Mars Global
Surveyor.

\"To see new gullies and other changes in Mars surface features on a
time span of a few years presents us with a more active, dynamic planet
than many suspected before Mars Global Surveyor got there,\" said
Michael Meyer, Mars Exploration Program chief scientist, NASA
Headquarters, Washington.

Two gullies appear in an April 2005 image of a sand-dune slope where
they did not exist in July 2002. The Mars Orbiter Camera team has found
many sites on Mars with fresh-looking gullies, and checked back at more
than 100 gullied sites for possible changes between imaging dates, but
this is the first such find. Some gullies, on slopes of large sand
dunes, might have formed when frozen carbon dioxide, trapped by
windblown sand during winter, vaporized rapidly in spring, releasing gas
that made the sand flow as a gully-carving fluid.

At another site, more than a dozen boulders left tracks when they rolled
down a hill sometime between the taking of images in November 2003 and
December 2004. It is possible that they were set in motion by strong
wind or by a \"marsquake,\" Malin said.

Some changes are slower than expected. Studies suggest new impact
craters might appear at only about one-fifth the pace assumed
previously, Malin said. That pace is important because crater counts are
used to estimate the ages of Mars surfaces.

The camera has recorded seasonal patterns of clouds and dust within the
atmosphere over the entire planet. In addition, other instruments on
Mars Global Surveyor have provided information about atmospheric changes
and year-to-year patterns on Mars as the mission has persisted. Daily
mapping of dust abundance in Mars\' atmosphere by the Thermal Emission
Spectrometer has shown dust over large areas during three Mars southern
hemisphere summers in a row. However, the extent and duration of dust
storms varied from year to year.

Mars Global Surveyor was launched Nov. 7, 1996; entered orbit around
Mars

Sept. 12, 1997; and returned the first Mars data from its science
instruments Sept. 15, 1997. Beyond its own investigations, the orbiter
provides support for other Mars missions, such as landing-site
evaluations, atmospheric monitoring, communication relay and imaging of
hardware on the surface. JPL, a division of the California Institute of
Technology in Pasadena, manages the mission for NASA\'s Science Mission
Directorate, Washington. JPL\'s industrial partner is Lockheed Martin
Space Systems, Denver, which built and operates the spacecraft.

For newly released images on the Internet, visit:

<http://www.nasa.gov/vision/universe/solarsystem/mgs-092005-images.html>

and
[http://www.msss.com/mars_images/moc/2005/09/20/](http://www.msss.com/mars_images/moc/2005/09/12/) 
.

For more information about NASA and agency programs on the Internet,
visit:

<http://www.nasa.gov/home>

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