Gusev Crater on Mars may have been an ancient lake bed on the Red Planet, based on new evidence obtained by the Spirit rover.

Comanche outcrop exhibits features that suggest water may have once been prevalent in the environment. The feature contains large quantities of magnesium-iron carbonate minerals. Carbonates, which are salts of carbonic acid, may been distributed by water in the ancient waterway.

"We looked more closely at the composition and geologic setting of Comanche and nearby outcrops. There's good evidence that low temperature surface waters introduced the carbonates into Comanche rather than hot water rising from deep down," said associate research professor Steve Ruff of Arizona State University.

Ancient volcanic ash called tephra started creating the Comanche outcrop. This ash, created in a nearby volcanic eruption, initially covered much of the Columbia Hills and the surrounding area.

"Comanche and a neighbor outcrop called Algonquin are remnants of the older and much more widespread tephra deposit. The wind has eroded most of that deposit, also carrying away much of the evidence for an ancient lake," Ruff stated in a press release.

Steve Ruff studied the information collected by the rover during its mission on the red planet.

Astronomers have long suspected Gusev Crater may have once held water, but the new analysis of data from the Spirit rover lends evidence to the theory. 

Spirit was set down in the Gusev Crater, since astronomers believed it may have been a large lake. When the rover sampled the bed, it discovered volcanic rocks, disappointing many people. Just two miles away from the landing site, the rover discovered geological formations that appeared to be formed by ancient hot springs. Water may have entered the crater from the large valley located south of the volcanic bed, carrying carbonate materials, which were left behind as the water evaporated.

"The wind has eroded most of that deposit, also carrying away much of the evidence for an ancient lake," Ruff stated.

Spirit landed on the surface of Mars in Jan. 4, 2004. The rover, designed to sample surface rocks in search of evidence for ancient water, went silent on 22 March 2010. That was the same year that the unusual chemistry of the outcrop was first detected by the Mars rover.

NASA is planning a new Mars rover, scheduled for the year 2020. The mission of this rover will be to search for signs of ancient life. The destination of this craft is yet to be determined, but a return to Gusev Crater is being considered. Geologists frequently return to sites after an initial survey, and a second mission to the crater would answer questions astronomers still have about the geological feature.

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