COURTESY UNIVERSITY OF HAWAII This infrared image of Mars' Terra Sirenum region was among thousands captured by the Thermal Emission Imaging System on NASA's Mars Odyssey orbiter. The blue areas of this map represent chloride salts that might have been left behind by water, concluded researchers led by University of Hawaii graduate student Mikki Osterloo.

UH finds water clues on Mars

Combing through thousands of infrared images of Mars pays off for a UH graduate student

Research by a University of Hawaii graduate student has provided new evidence that Mars once had abundant water and the potential for some sort of life.

Student Mikki Osterloo, who led a research team, found salt deposits by looking at about 20,000 images from an orbiting camera that were processed to reveal, in false colors, compositional differences on the Martian surface. The deposits were reported in this week's journal Science.

Osterloo said the salts indicate there was water on Mars, either standing or evaporating. "It could have been ground water influx that barely touched the surface and evaporated."

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GEORGE F. LEE / GLEE@STARBULLETIN.COM University of Hawaii graduate student Mikki Osterloo, right, stands in front of a multispectral THEMIS infrared image of the Terra Sirenum region of Mars. Her team's research indicates that areas on the map are chloride salts that might have been left behind by water once present there. With her are Institute of geophysics and planetology professors Scott Anderson and Vicky Hamilton.

A research team led by a University of Hawaii graduate student has identified chloride salt deposits on Mars, providing new evidence that it once had abundant water and possibly some form of life.

Student Mikki Osterloo said the salts indicate there was water on Mars, either standing or evaporating. "It could have been ground water influx that barely touched the surface and evaporated."

The deposits were reported in this week's journal Science by Osterloo and seven co-authors, including Vicky Hamilton, second author, and Scott Anderson, Osterloo's adviser. Both are associate researchers in the Hawaii Institute of Geophysics and Planetology.

The researchers think the deposits formed 3.5 billion to 3.9 billion years ago.

The chloride minerals were found in about 200 places in the Red Planet's most ancient rocks in the southern highlands, said Osterloo, who is working on a doctorate degree in the Department of Geology and Geophysics, School of Ocean and Earth Science and Technology.

They had been overlooked because they have no distinctive spectral characteristics, she said in an interview. She found them by going through thousands of infrared images from the Thermal Emission Imaging System on NASA's Mars Odyssey orbiter.

"I think only a graduate student would have time to do that," she said. "I was really lucky. It was very much a team effort."

She said the images were processed to reveal compositional differences on the Martian surface. "I started noting these sites because they showed up in bright blue in one set of images, green in a second set and yellow-orange in a third."

Anderson said the discovery "is opening a new chapter in our understanding of how Mars evolved. "It's quite exciting when a student identifies a new feature in a data set like THEMIS and is able to run with it in the way Mikki has."

He said Osterloo looked at about 20,000 images, going through the entire data set from THEMIS, a camera developed by Arizona State University for visual and infrared wavelength images. It can see details on the Martian surface as small as 330 feet wide.

Hamilton said one reason researchers didn't detect the chloride mineral deposits previously is they are fairly small plots and a relatively high resolution instrument is needed to see them. Some of the largest are about 10 square miles; the smallest ones are about 0.4 square mile, she said.

Anderson said rocks and minerals look black or gray most of the time in visible light. It's unlikely the sites are remnants of a global ocean because they're not connected, she said.

"When we look at the geologic context of deposits, they tend to occur in local depressions," Hamilton said; that suggests either the water ponded in low areas or the groundwater table rose to the surface and evaporated.

She said Osterloo's discovery supports other evidence of water on Mars. "It helped us fill out the picture of water on Mars."

"It's very exciting," Osterloo said. "More work needs to be done on the whole theory of wet Mars. Another piece of evidence indicates it's quite possible the climate was much more wet early on in Mars' history."

She plans to continue looking at images from the THEMIS camera and is collaborating with another team to collect data from an instrument on the Mars reconnaissance orbiter.