UH study deepens Mars
water mystery

A region on Mars' surface with the mineral olivine is four times larger than estimated, again raising the question of whether water existed on the red planet, Hawaii and Arizona planetary geologists say.

Scientists are eager to find out if water was on Mars because it is considered a key element for life, and large quantities of olivine indicate the lack of water.

The findings of professors Victoria Hamilton of the University of Hawaii Institute of Geophysics and Planetology and Philip Christensen of Arizona State University are reported in the June issue of the journal Geology.

Olivine is the most susceptible mineral to weathering by water, yet the large quantities seen on Mars are in an ancient area 3 billion to 4 billion years old, Hamilton said yesterday.

This suggests the rocks might have been protected from any water on the surface of Mars or possibly were never exposed to any, she said.

She said olivine rapidly turns into other minerals in the presence of water under many conditions, "so the preservation of all this olivine in a very old region of Mars is intriguing."

At least some of the rocks were erupted on Mars' surface where they might have been exposed to more water and weathering than if they had been forced into the subsurface as previously proposed, the researchers found.

Hamilton and Christensen are studying high-resolution infrared data from the space agency's Mars Odyssey and Mars Global Surveyor spacecraft. They have NASA research funding.

Christensen is responsible for a two-camera thermal imaging system called THEMIS on Odyssey that identifies the mineral content of rocks and other surface materials.

He also has a thermal emission spectrometer in orbit around Mars on the Global Surveyor. It produced the first global mineral map of Mars with measurements of the infrared signatures of minerals on the surface.

The imaging spectrometer on Odyssey will identify where wet environments once existed on Mars -- places where there could be past or present signs of life.

Hamilton and Christensen are trying to understand what the rocks are on Mars and what they say about the planet's geologic history. She said they are trying to figure out where meteorites on Earth came from Mars, which would reveal a lot about the planet.

About a year or two ago, the researchers identified places on Mars with infrared spectra like meteorites found on Earth, Hamilton said. With higher-resolution data available, they are getting more details about Mars' geology, she said.

In the past, places nearby were covered with dust, which they cannot see through, she said.

"We can't see through dust with the spectrometer, but we can get more spatial information about the temperature of rocks and, basically, using the temperature data, are able to figure out that olivine-rich rock continues under the dust to cover a bigger area than we realized before."

Now that they know the detailed distribution of the olivine-rich rocks, Hamilton said, "We've really got to look in detail and find any minerals that suggest this olivine has weathered and what was the chemistry involved."