Artist's concept of Mars Exploration Rover
Artist's concept of Mars Exploration Rover
With just over a year to go before NASA's twin Mars Exploration Rovers land on the red planet, members of the science team are previewing the mission's goals and candidate landing sites at a special session of the American Geophysical Union meeting in San Francisco.

"The twin rovers will be able to travel the distance of several football fields during their missions. They will carry sophisticated instruments that effectively make them robotic geologists, acting as the eyes and hands of the science team on Earth," said Dr. Mark Adler, mission manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "We are very busy at JPL building and testing the two rovers and the spacecraft that will land them safely on Mars."

Remote sensing instruments will be mounted on a rover mast, including high-resolution color stereo panoramic cameras and an infrared spectrometer for determining the mineralogy of rocks and soils. When interesting scientific targets are identified, the rovers will drive over to them and perform detailed investigations with instruments mounted on a robotic arm.

Rover instruments include a microscopic imager, to see micron-size particles and textures; an alpha-particle/x-ray spectrometer, for measuring elemental composition; and a Moessbauer spectrometer for determining the mineralogy of iron-bearing rocks. Each rover will carry a rock abrasion tool, the equivalent of a geologist's rock hammer, to remove the weathered surfaces from rocks and analyze their interior.

"All the instruments on the payload are undergoing intensive calibration and test activities in preparation for flight," said Dr. Steve Squyres, principal investigator for the science payload at Cornell University, Ithaca, N.Y.

"Once at Mars, the instruments will be used, together with the rover's ability to traverse long distances, to study the geologic history of the two landing sites," Squyres explained. The scientific focus of the mission is to investigate what role water played there, and to determine how suitable the conditions would have been for life.

NASA scientists are in the process of picking the landing site for each rover. Four sites look the most promising. "Three of the sites, Terra Meridiani, known as the Hematite site, Gusev, and Isidis show evidence for surface processes involving water. These sites appear capable of addressing the science objectives of the rover missions: to determine if water was present on Mars and whether there are conditions favorable to the preservation of evidence for ancient life," said Dr. Matt Golombek, landing site scientist at JPL. The fourth site, Elysium, appears to contain ancient terrain, which may hold clues to Mars' early climate when conditions may have been wetter.

The launch period for the first rover opens May 30, 2003, and the second rover's launch period opens June 25, 2003. The first rover will reach Mars January 4, 2004, and the second arrives January 25, 2004. Each rover will have a primary mission lasting at least three months on the martian surface.

The Jet Propulsion Laboratory manages the Mars Exploration Rover mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology, Pasadena.

Pictures of the rovers at JPL can be viewed at:

More information about the mission is on the Internet at:

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