ASU geologists suggest Mars features are result of meteorite strikes, not of evapor...( arly interesting feature found at the O...)

arly interesting feature found at the Opportunity landing site are little spheroid like concretions, or globules, of material. Initially, scientists believed they were artifacts of water interacting with the ground as it moves through the rocks. But in order to make as many spheroids as they found, it would take large amounts of groundwater to be present and "these things need to grow within rock. We didn't see any evidence of this," said Knauth, who has been studying concretions on Earth for 35 years.

"They were absolutely perfect little spheres," he said. "These turn out to be abundant in base surges. They form like little hailstones. They are the same shape, the same size and the same uniform distribution, which concretions don't have."

Knauth explains that there is plenty of evidence of past water on Mars and that there is a fair likelihood that some forms of life may have existed on the Red Planet. But if the team's theory is correct, and the surface features of Meridiani Planum were caused by meteorite strikes and not a large lake, then the scientists need to be more creative in where they focus the next steps of their exploration for evidence of life forms, Knauth said.

Knauth said clues may lie in Martian rocks.

"If we know anything about Mars it is that it has been pounded unmercifully by meteorites," he added. "We just need to live with it and take advantage of it. Meteorites are excavators, they throw rock around all over the planet and I think some of those are juicy astrobiological targets."

He said most every rock on Mars is cracked and if there was microbial life on the planet, microorganisms could be picked up by the wind and driven to different parts of the landscape. They eventually could lodge in the cracks of rocks and have calcium carbonate and other salts entomb them."

He added that one of the meteorites from Mars has such carbonate in cracks and possibly contains evidence of past life. Cracks
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Contact: Skip Derra
skip.derra@asu.edu
480-965-4823
Arizona State University
21-Dec-2005

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