Mineral build-up may indicate former shoreline
Three University of Arizona researchers have helped lend credence to the hypothesis that Mars once had oceans.
In a paper to be published in Planetary and Space Science, senior hydrology research specialist James Dohm, UA regents Professor Victor Baker and Professor William Boynton of the Lunar and Planetary Laboratory, write that mineral deposits near what appear to be shorelines show that the oceans existed more than 2 billion years ago.
“It’s consistent with this ocean potential – it doesn’t confirm it, necessarily,” Dohm said. “I think it’s a significant piece of the puzzle.”
By analyzing the soil above and below the “shoreline” with a gamma ray spectrometer, the team found different concentrations of thorium, potassium and iron above and below the shore.
Since high concentrations of those minerals are found at higher elevations on Mars but not in volcanic soil, the finding supports the theory that the soil was deposited by erosion and left in a large body of water, Dohm said.
Proving large bodies of water existed on the red planet is difficult for several reasons. On Earth, shore erosion is largely caused by tides, which are caused by the moon’s gravitational pull.
“On Mars you have smaller moons. You don’t have the tidal forces,” Dohm said, which makes it tough to see shorelines.
And because Mars is much colder than Earth, the oceans could have been covered in ice, which would block wave action that creates a distinctive look.
The scientists used the spectrometer aboard Odyssey, an orbiter that reached Mars in 2001 and will continue to send data at least through 2010.
The instrument allowed the team to “see” soil about a foot under the surface, which is often covered in volcanic dust that masks the deeper soil’s composition, Dohm said.
The research supports the theory that Mars had at least two oceans – one about 2 billion years ago the size of North America and an older one twice that size.
“This older body of water would have been about 3 1/2 billion years ago,” Dohm said.
The UA scientists were co-authors on the study, along with scientists from Italy, Spain, South Korea and Canada.
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