Posted on: Saturday, May 28, 2005

Olivine on Mars found in vast area

By Audrey McAvoy
Associated Press

A study co-authored by a University of Hawai'i professor has concluded that an area of Mars has much larger than believed deposits of the mineral olivine, offering clues about water — or the lack of water — on the Red Planet.

While Mars today is a dry and cold world, river channels and other water-carved features suggest it may have had a more hospitable past.

Since water is a necessary ingredient for life, proof that the substance either existed on Mars or never did would answer one of humanity's enduring questions about the planet.

Victoria Hamilton, an assistant professor at the Hawai'i Institute of Geophysics and Planetology, concluded from data obtained by the Mars Odyssey spacecraft that larger-than-earlier-believed amounts of olivine sit in a volcanic rock on Mars.

Since olivine weathers and rapidly turns into other minerals in the presence of water, the finding of the large deposits may mean that this area of Mars never had much water, Hamilton said.

The other hypothesis is that the area had water, but the water carried the minerals made from its interaction with olivine away when it washed through, leaving no trace of water behind, she said.

A green mineral sometimes used in jewelry, olivine is found in volcanic regions on both Earth and Mars. Green Sands Beach near South Point on the Big Island gets its color from olivine crystals.

Hamilton said the Mars bedrock rich with olivine was previously believed to be as large as 12,000 square miles, but turned out to be almost four times bigger at about 45,000 square miles.

"It's like you've been standing on Kilauea but you've suddenly discovered four more volcanoes," Hamilton said. "There's so much more than we realized."

Hamilton's study, co-written with Philip Christensen of Arizona State University, appears in the June edition of the journal Geology.

The researchers studied high-resolution infrared data from NASA's Mars Odyssey spacecraft, which has been orbiting the planet since 2001.

On Earth, olivine can coexist with water because volcanic activity that produced it has taken place more recently than on Mars, leaving less time for it to be weathered or washed away.

The olivine on the Big Island's Green Sand Beach will be washed away eventually, but not soon on the human scale of time, Hamilton said.