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Looking for fossils of Martian life.

On Earth, the crusty mineral deposits surrounding such geysers as Yellowstone's Old Faithful are chock full of fossilized bacteria and other simple organisms. Now, two planetary scientists suggest that the regions on Mars likely to have harbored now-extinct geysers or springs represent promising places to look for imprints of life on the Red Planet.

Researchers have speculated that while present conditions on Mars cannot support life, organisms may have existed there in the distant past, when water might have been more plentiful. For example, scientists have suggested that lakes may have covered parts of the planet more than 2 billion years ago; today those regions might hold fossils from that era.

But David J. Des Marais of NASA's Ames Research Center in Mountain View, Calif., and M. R. Walter of Macquarie University in Sydney, Australia, suggest that other places on Mars appear more likely to harbor fossils. They assert that hot springs -- created when underground water rises to the surface after flowing through volcanic rock--may once have been common on the planet. Such springs, illuminated by sunlight and enriched in nutrients and minerals from dissolved rock, could have sustained simple organisms, Des Marais says. Moreover, when the springs cooled, silica-rich minerals in the water would have solidified on the Martian surface, trapping organisms in the cooling water. Thus, springs could have served as a nutrient source and preservation agent for primitive life.

Some scientists note that if springs ever existed on Mars, they probably covered fairly small surface areas. Their size might make it difficult to identify sites of extinct springs -- and to hunt for fossils. Though NASA's Mars Observer can't search for fossils, it does carry a thermal emission spectrometer that can detect silica-rich mineral deposits just a few kilometers wide, Des Marais says (SN: 9/19/92, p. 181). Some of those deposits may represent extinct springs or geysers, he adds. Upcoming missions, Des Marais says, "may open our eyes" to the notion to extensive geysers on the planet.
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Title Annotation:researchers say once-plentiful water on Mars may have sustained life
Author:Cowen, Ron
Publication:Science News
Article Type:Brief Article
Date:Sep 26, 1992
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