Latest Mars find adds to water theory

Rover Opportunity believed to be sitting on the former shoreline of a salty sea.

By Gary Robbins

March 24, 2004

The Mars rover Opportunity appears to be sitting on what once was the shoreline of a salty sea, a discovery that greatly increases the possibility that the essence of known life - water - was plentiful on the planet's surface, scientists said Tuesday.

"If we are correct in our interpretation, this was a habitable environment," said Steve Squyres, the Cornell University researcher who leads the evaluating data from Opportunity and its sister rover, Spirit.

The discovery was based on a review of close-up images Opportunity took after it landed inside a shallow crater at Meridiani Planum. It then began looking at a rock outcropping about as high as a street curb. The outcrop features curvy patterns and concentrations of salt that indicate the rocks formed from "deposits at the bottom of a body of gently flowing saltwater," said the National Aeronautics and Space Administration, which revealed the findings Tuesday.

"If you have an interest in searching for fossils on Mars, this is the first place you'd want to go," said Ed Weiler, NASA's associate administrator for space science. Squyres agreed that the rocks represent an excellent tomb for ancient traces of biological material. But he noted that Opportunity's microscopic imager isn't powerful enough to detect microbial fossils. A more sophisticated rover - possibly the planned Mars Science Laboratory in 2009 - would have to mine for fossils.

Researchers currently don't have enough data to figure out how large or deep the sea was at Meridiani or when it existed. But they are dispatching Opportunity to Endurance, a nearby crater where larger outcrops might help resolve the matter.

The latest news adds to mounting evidence that at least parts of the frigid planet were once warmer and wetter, and thus more amenable to life.

Three weeks ago, NASA announced that Opportunity had found signs that some of the rocks in the crater where it landed Jan. 24 had once been soaked in water. It was initially unclear whether the water helped form the rocks, and whether the rocks encountered water underground or at the surface.

Opportunity - which uses about as much power as a curling iron - clarified the situation by taking scores of additional photographs. A mosaic of those images revealed that some of the rocks formed from sediments whose surface was etched with telltale curves, or cross bends, by water flowing above ground.

Such rocks can form along shorelines and salt flats like those found in desert basins and the edge of oceans on Earth, said John Grotzinger, a researcher from the Massachusetts Institute of Technology.

The scenario intrigues Greg Weiss, an organic chemist at the University of California, Irvine.

"Salts help give structure to molecules, the building blocks of life," said Weiss, who cautioned that there is insufficient evidence to conclude whether life ever arose at Meridiani.

Opportunity could produce revelations far beyond those expected when it examines rocks at Endurance crater. NASA said Monday that it will be able to extend the life of both rovers far beyond late spring, possibly keeping the "geobots" going until September. It's also possible that Opportunity will be able to inch its way to hills about 1.6 miles away. Originally, NASA said Opportunity and Spirit had a maximum range of about 4,000 feet.