Opportunity finds evidence of a salty Martian sea, Squyres reports

By Blaine P. Friedlander Jr.

WASHINGTON, D.C. -- The robotic rover Opportunity seems to be surveying the shoreline of a salty Martian sea, an environment that could have supported life, Cornell astronomer Steven Squyres told a NASA press conference March 23.

Squyres

"We think Opportunity is parked on what was once the shoreline of a salty sea on Mars," said Squyres, Cornell professor of astronomy and the principal scientist on the Mars rover mission, at a press conference at the space agency's headquarters in Washington, D.C.

As he spoke, Opportunity had just completed its slippery climb out of "Eagle crater" on a vast plain called Meridiani Planum, where it had come to rest after its bounce-down landing Jan. 25.

So far mission scientists cannot estimate how much water once covered the area, or when the water evaporated. But Squyres said he is certain that life could have existed.

The evidence for flowing water exists in telltale patterns like crossbedding and festooning in the sedimentary rocks around Eagle crater. These patterns have emerged in Opportunity's images as angular and curved layering within rocks and have smile-shaped curves, produced by shifting of the sediments under gentle water current, according to Squyres.

He said that this kind of sediment offers excellent capability for preserving evidence of any biochemical or biological material that might have been in the water. "This is a habitable environment on Mars and it was suitable for life," said Squyres. "This environment has the potential for the preservation of evidence of life and [to] trap whatever was in the water."

This image mosaic, from navigation and panoramic cameras aboard the Mars rover Opportunity, shows a view of the "Eagle crater," where the rover came to rest after its bounce-down landing Jan. 25. This week the rover spent two Martian days, or sols, ascending the slippery slopes to the crater's rim, enabling the cameras to look back at the rover lander, visible in the center of the image. The track marks seen in the crater, which is about 22 meters (72 feet) in diameter, reveal the rover's progress. NASA/JPL/Cornell

Evidence of chlorine and bromine in the rocks also indicates an oceanic environment. Rover scientists, including Squyres, presented some of that news three weeks ago as evidence the rocks had at least soaked in mineral-rich, possibly underground, water after they had been formed.

James Garvin, lead scientist for Mars and lunar exploration at NASA headquarters in Washington, noted at the latest press briefing: "We planned for the Mars Exploration Rover Project to look for evidence like this, and it is succeeding better than we had any right to hope. Someday we must collect these rocks and bring them back to terrestrial laboratories to read their records for clues to the biological potential of Mars."

To analyze hints of crossbedding, mission controllers programmed Opportunity to move its robotic arm more than 200 times in one day, taking 152 microscope pictures of layering in a rock dubbed "Last Chance." Squyres said he doubts that fossil forms of microbial life will emerge on this Mars rover mission because there is not enough resolution in the microscopic imager aboard both rovers to make this detection.

To date, Opportunity and its twin rover, Spirit, have taken 18,000 images, a quarter-million measurements, and prepared 20 gigabits of data. Engineers at NASA's Jet Propulsion Laboratory in Pasadena, Calif., the mission manager, expect the rovers to operate several months longer than the initial three-month estimate.