Inside Victoria Crater: View of Martian stratigraphic layer informally named "Lyell", the lowermost of three layers found inside of Victoria Crater by the Mars rover Opportunity.
Courtesy NASA/JPL-Caltech/Cornell UniversityThe science gathered so far by the two Martian rovers, Opportunity and Spirit, suggests the Red Planet may have been a bit too inhospitable to support even the toughest forms of life.

Although strong evidence of water (at least in the planet’s past) has been found on Mars, recent assessment of the data shows it contains a much higher salt content than expected and that practically puts the kibosh on hopes of any microbes flourishing there.

Opportunity spent time recently examining strata exposed on the inner wall of Victoria Crater. NASA scientists hoped it would show a record of the ground surface as it existed prior to impact that created the crater. But analysis suggests it to be the top of an underground water table, and after reassessing earlier data, and performing some computer modeling, researchers think the environment may have been too harsh to support life.

"At first, we focused on acidity, because the environment would have been very acidic," said Dr. Andrew Knoll, a Harvard biologist who is a member of the rover science team. "Now, we also appreciate the high salinity of the water when it left behind the minerals Opportunity found. This tightens the noose on the possibility of life."

Knoll spoke at the annual meeting of the American Association of the Advancement of Science (AAAS) in Boston.

"Life at the Martian surface would have been very challenging for the last 4 billion years. The best hopes for a story of life on Mars are at environments we haven't studied yet -- older ones, subsurface ones," he said.

Lower, more ancient, geological layers may hold a more hospitable picture of a less briny Martian environment, but the current rover missions aren’t set up to examine that.

"Our next missions, Phoenix and Mars Science Laboratory, mark a transition from water to habitability -- assessing whether sites where there's been water have had conditions suited to life," said Charles Elachi, at NASA's Jet Propulsion Laboratory. "Where conditions were habitable, later missions may look for evidence of life."

The Phoenix lander is expected to reach Mars on May 25, 2008 in an area farther north on the planet where it will study the icy subsurface for viable signs of life. The Mars Science Laboratory will launch in the fall of 2009.

Opportunity and Spirit, the two rovers operating presently on opposite sides of the Mars, were sent there with one mission in mind: finding evidence of water. The missions were expected to last a mere three months, but have far surpassed that due to the robots’ high endurance, and problem-solving ingenuity of NASA engineers back on Earth. The robots are now entering their fifth year exploring the Martian surface.

LINKS and INFO
NASA press release
BBC story
Mars info
More about Mars (with less salt)

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