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Planetary geology
Mars once drenched in water

Scientists from NASA’s Mars Exploration Rover mission projects announced March 2 that they had found definitive evidence for “a lot of water” at some point in the planet’s history. Principal investigator Steve Squyres of Cornell University said water could have “drenched” the surface, possibly creating a habitable landscape for some time.

“Ever since Opportunity touched down,” Squyres said in a press conference at NASA headquarters in Washington, D.C., “we have been puzzling over it.” The layered rocks in the crater where the rover Opportunity landed in January hold “tantalizing clues,” he said, to answer the question: “Were these altered by liquid water? The answer to that is definitely yes.”

Squyres emphasized that the researchers do not know how long or when the water may have been present, or if the water was at the surface or existed as groundwater. Nevertheless, he said, the team found four criteria at the outcrop that pin down evidence for liquid water present in large quantities.

The strongest of those pieces of evidence is weathered-out forms in the sediment that look like sulfur hydrate crystals, shaped approximately as gypsum is on Earth. “For sulfide hydrates,” Squyres said, “you have got to have water.”

The team stressed that their results come from a very small section of Mars. “We’re talking about 20 centimeters” of outcrop thickness, Squyres said. John Grotzinger, geologist for the Mars rover team, said that seeing other sites will be important, including a future trip to a part of the outcrop that seems to have crossbedding, a kind of sedimentary layering that may be from particle deposition by flowing wind, air or water currents.

However, the evidence from Opportunity’s first outcrop confirms what previous observations of hematite deposits indicated — Mars was once a warm planet with a lot of liquid water on or near its surface.
Read more about what the Mars rover team found at Geotimes online.

Naomi Lubick

Links:
"NASA says Mars once drenched in water," Geotimes Web Extra, March 2, 2004


For more Geotimes coverage of Mars, click here.

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