Sojourner's pictures even show dried-up puddles. This tells scientists that at the time of the floods, temperatures on Mars were too warm for the water to freeze. It uses light filters to determine the chemicals in rocks. The iron in its soil combined with oxygen long ago. Most of that oxygen is now part of the carbon dioxide in the planet's atmosphere.
Pathfinder is the first of ten planned missions to Mars.
NASA will send two spacecraft every 26 months, when Earth and Mars are nearest to each other. Mars Observer stopped sending back data just as it neared Mars. It may have exploded. Scientist learned little from that costly mission, but they have already learned a great deal from Pathfinder . Powered by solar panels, tiny Sojourner has sent back information that will keep scientists busy for years.