After 100 days of roving, Spirit and Opportunity find mission a grind

By Blaine P. Friedlander Jr.

In a workroom at the Jet Propulsion Laboratory, Jim Bell (right), Cornell associate professor of astronomy, works with media technicians in selecting rover Pancam images of Mars, prior to the March 5 press briefing. Bell is the leader of the Pancam team that processes high-resolution images from the rovers Cornell News Service photo by Blaine Friedlander Jr. Copyright © Cornell University

PASADENA, Calif. (March 5) -- On a combined 100th day of roving for the rovers Spirit and Opportunity , Mars is slowly yielding its aquatic history -- from two sides of the planet -- to the discerning eyes of geologist-astronomers back on Earth.

Days after the rover Opportunity unveiled clues of water from a crater at Meridiani Planum, the rover Spirit at Gusev crater on the other side of Mars is finding different kinds of rock and a different kind of moisture, it was reported at a press briefing at the Jet Propulsion Laboratory (JPL) here today.

Using the Cornell-developed rock abrasion tool, or RAT, scientists made a small hole and peered into a suitcase-sized rock at Gusev, dubbed Humphrey. They believe they have found an igneous rock much tougher to grind with the RAT than the sedimentary bedrock found at Meridiani Planum.

At the press briefing, Ray Arvidson, of Washington University in St. Louis, the deputy principal scientist on the mission, displayed images the RAT-scored interior of Humphrey showing where heartier mineral deposits lay. These deposits, he said, likely were delivered through fractures in the rock by an "aqueous fluid." He noted, "When rocks are made on Mars, fluids are involved."

The tool making these findings possible is the RAT, the diamond-tipped grinder designed by Steven Squyres, Cornell professor of astronomy and the principal science investigator on the Mars rover mission, and Paul Bartlett '99 , a Cornell engineering alumnus, who works for Honeybee Robotics in New York City.

Before and after: Grinding with the rock abrasion tool (RAT) reveals that the inner structure of a rock in Opportunity's crater wall is much the same as its surface, and the grinding stirs up particles of what may be hematite. Click on the image for a high-resolution version (1050 x 563 pixels, 745K)

"The RAT has generated some fascinating data," said Jim Bell, Cornell associate professor, and the lead scientist on the panoramic camera, or Pancam, team, at the briefing. The panoramic camera, using its infrared filter, has sent back images showing minerals consistent with a wet area.

At Gusev crater, the Spirit's RAT yesterday ground away a centimeter at a time, leaving a fine dust from the outer layer of Humphrey rock. Based on filtered Pancam images, Bell believes the dust is hematite, a mineral often associated with the presence of water.

Matt Wallace, the JPL mission manager for Opportunity, informed reporters that today was the Spirit's 60th Martian day, or sol, and Opportunity's 40th, giving the two vehicles a combined 100 days of roving. "We've had a terrific 100 days on Mars," he said. "We seem to be hitting our stride because we're thinking about longer-term issues, and it's a nice feeling to get into that mode as our mission seems to be getting even more complex."

The Mars geologists have a clear talent for nicknames. So while Spirit has about two weeks before its reaches the rim of Bonneville crater, Opportunity has left Last Chance rock and is now headed for the Berry Bowl and Slick Rock on the western side of the crater. Wallace said that the science and engineering teams are beginning to contemplate Opportunity's departure strategy from the small crater at Meridiani Planum in which it landed on Jan. 25.

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