Salt on Mars Spotlights Search for Life

March 20, 2008 -- Scientists have discovered salt deposits on the surface of Mars, indicating that water was once plenty and pointing to sites that could provide evidence of past life, a study said Thursday.

The deposits were discovered by a team of scientists led by Mikki Osterloo at the University of Hawaii using thermal images from the orbiting Mars Odyssey spacecraft, according to research in the March 21 issue of the journal Science.

The researchers have discovered some 200 separate salt deposits in the southern hemisphere of Mars and at mid- to low-level latitudes. The scientists described the terrain as ancient and heavily cratered.

"Many of the deposits lie in basins with channels leading into them," said journal co-author Philip Christensen from the University of Arizona.

"This is the kind of feature, like salt-pan deposits on Earth, that's consistent with water flowing in over a long time," he added.

According to Osterloo, the deposits "range in area from about one square kilometer (0.4 square mile) to about 25 square kilometers (about 10 square miles)."

The deposits appear to be disconnected, so "we don't think they all came from one big, global body of surface water," she said.

Instead "they could come from groundwater reaching the surface in low spots. The water would evaporate and leave mineral deposits, which build up over years," she said.

The scientists estimate that these deposits were probably formed between 3.9 and 3.5 billion years ago.

There are several geological indications that Mars, in its past, had hotter, more humid weather than the cold and dry conditions it has today.

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