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

[Ron Baalke]

MEDIA RELATIONS OFFICE
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NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
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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/  .

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

http://www.nasa.gov/home

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