[meteorite-list] Orbiter's Long Life Helps Scientists Track Changes on Mars

From: Darren Garrison <cynapse_at_meteoritecentral.com>
Date: Wed Sep 21 12:41:09 2005
Message-ID: <v933j19mnam58faamsumvc8vcaq1ortj2i_at_4ax.com>

http://mars.jpl.nasa.gov/mgs/newsroom/20050920a.html

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.
Received on Wed 21 Sep 2005 12:42:27 PM PDT