Mars' Gusev crater may have once held a lake: Scientists
Researchers have said that Mars' Gusev crater may have held water more than once.
The findings have been made by a team led by Steve Ruff, associate research professor at Arizona State University's Mars Space Flight Facility in the School of Earth and Space Exploration.
When Spirit began to explore the crater, scientists found Gusev's floor was paved not with lakebed sediments, but volcanic rocks. Less than two miles away however stood the Columbia Hills, 300 feet high. When Spirit drove up into them, it indeed discovered ancient rocks that had been altered by water. But to scientists' chagrin, no lake sediments were among them. Instead, scientists discovered evidence of hydrothermal activity, essentially hot springs like those in Yellowstone National Park.
The findings have been helped by Columbia Hills rock outcrop dubbed Comanche, which is unusually rich in magnesium-iron carbonate minerals, a discovery made in 2010 that Ruff played a major role in making. While Comanche's carbonate minerals were originally attributed to hydrothermal activity, the team's new analysis points to a different origin.
Comanche started out as a volcanic ash deposit known as tephra that originally covered the Columbia Hills and adjacent plains. This material, Ruff explains, came from explosive eruptions somewhere within or around Gusev.
Then floodwaters entered the crater through the huge valley that breaches Gusev's southern rim. These floods appear to have ponded long enough to alter the tephra, producing briny solutions. When the brines evaporated, they left behind residues of carbonate minerals. As the lake filled and dried, perhaps many times in succession, it loaded Comanche and its neighbor rocks with carbonates.
The study has been published in the journal Geology.
(Posted on 10-04-2014)