Is Mars letting us down? In the 1980s and early 1990s, many planetary scientists got the sinking feeling that the Red Planet wasn't living up to humanity's expectations. Its surface was lifeless, its volcanoes extinct. Evidence of an Earth-like past was looking shaky. When I entered graduate school in planetary science during this period, I was discouraged from doing research on Mars, as the data from the Viking spacecraft of the mid-1970s had been thoroughly picked over. Follow-up missions from the U.S. and the Soviet Union floundered. Scientists found themselves pitted against "Face on Mars" conspiracy theorists in television debates.

Even through these dark years, veteran researcher William K. Hartmann held that Mars was not, in fact, geologically dead. He reasoned that some of the terrain was so fresh, so free of meteor craters, that at least some of the volcanoes were not extinct, merely dormant. It was a minority view--but no longer. New space missions have found signs not just of recent volcanism but of glaciers, liquid water and periodic climate change. Things are looking up again for the Red Planet, and Hartmann's latest book encapsulates this understanding.

   
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