The opening salvo includes NASA's Mars Global Surveyor, to launch Wednesday, and the Mars Pathfinder mission, launching Dec. 2. Sandwiched between those is launch of Mars 96, a Russian-led international mission equipped with two U.S. instruments. Water is vital for life as humans know it and, not inconsequentially, a natural resource that could be broken down to produce breathing air and rocket propellants for human explorers. Larger than the moon but smaller than Earth, Mars would be the first stop on a journey into the outer reaches of the solar system. Past U.S. robotic missions reveal a desertlike world with a thin, cold atmosphere of carbon dioxide, a rocky, reddish surface, towering inactive volcanoes and an ugly gash that dwarfs Earth's Grand Canyon.
Ice caps come and go from the polar regions as the seasons change.
Embossed on the landscape of Mars' northern hemisphere are tracings of ancient shorelines and long river valleys, suggesting that water in the form of lakes or oceans and flowing streams once was plentiful. The fact is we don't know. Experts believe its disappearance accompanied a puzzling climate change. Surface geology appears as if it underwent a period of intense erosion followed by a long quiescent period. It is possible, Carr believes, that Mars retains water, either frozen on the surface but camouflaged by rock and dust, or still liquid but channeled into subterranean lakes by long ago meteor hits.