The finding is a vein of gypsum, a mineral that forms in the presence of liquid water that has been dubbed Homestake. The vein of ore is "almost as wide as a thumb and a few tens of centimeters long," said geologist Steve Squyres of Cornell University at a meeting of the American Geophysical Union in San Francisco. Opportunity has found an association with water and minerals that Mars had before, but these findings were in sandstones. Before consolidating the rock, the grains of the stones could have flown many miles from their sources, hiding history minerales. By contrast, the Homestake vein is found in the rocks, which means that "these things are formed here, "said Squyres, principal investigator for the mission Rover.
"In the ancient past of Mars, there was a fracture in the rock. The water flowed through it. Gypsum precipitate. There is no ambiguity about this, "he said.
"This is the most powerful piece of evidence for liquid water on Mars has been found by Opportunity," Squyres said.
The vein of gypsum was found in one place, informally known as Cape York, on the edge of the 14-kilometer wide crater (23 km wide) Endeavour.
Gypsum bands like Homestake are not the only signs of water along strike.
Orbiting instruments have chemical signatures of smectite, a clay form, which is another mineral associated with water, said rover team member Ray Arvidson of Washington University in St. Louis.
Moreover, water-related minerals previously found by the rover had suggested a high acid content of the environment.
However, gypsum is formed under much more neutral than could have been friends for life, Squyres of Cornell said. ADS HERE
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