Return to the Red Planet

WASHINGTON--After a devastating loss 3 years ago, NASA is about to make another try for Mars. The Global Surveyor satellite, set for launch on 6 November, is designed to probe the geology and climate of Earth's closest known planetary cousin.

Surveyor is scheduled to reach the Red Planet in September 1997 and complete an orbit every 2 hours for at least 687 days--one Martian year. Beginning in March 1998, the satellite's cameras and other instruments will map the surface, including such features as the seasonal advance and retreat of the polar ice caps as well as channels cut eons ago. Scientists expect that a flood of data over the 2-year mission--some 600 billion bits--will help them to better understand Martian geology and to reconstruct the climate changes that transformed what may once have been a warm, wet planet into the cold desert it is today. One thing Surveyor is not expected to do is shed light on the debate over whether life may have existed on Mars.

The mission will be NASA's first trip to Mars since the agency lost radio contact with the $1 billion Observer satellite shortly before it was to enter Mars orbit in August 1993. Surveyor is in many ways a chip off the lost block. Most of Surveyor's instruments are Observer backups, which will allow it to carry out 80% of Observer's planned investigations, says Arden Albee, a Surveyor project scientist from the California Institute of Technology. The recycling has kept Surveyor slightly under its $155 million budget.

Surveyor is the first of at least eight launches in NASA's planned 10-year exploration of Mars. The next NASA launch--the Mars Pathfinder scheduled for 2 December--and Russia's Mars '96, slated for 16 November, will carry probes that are supposed to land on the surface and survey it.

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