Wednesday, July 6, 2011

Possibility for life on Mars found by scientists on Earth



The Mars Science Laboratory rover, Curiosity, undergoes mobility testing inside the Spacecraft Assembly Facility to prepare it for its fall 2011 launch

Read more: http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2011/07/05/MN3I1K5KK3.DTL#ixzz1RKTcGViC


Possibility for life on Mars found by scientists
David Perlman, Chronicle Science Editor

Wednesday, July 6, 2011

All it took was a hungry scientist to stop for lunch in the Mojave Desert, and suddenly there was a new prospect for seeking signs of life on Mars.

Space researcher Christopher P. McKay of NASA's Ames Research Center in the Santa Clara County city of Mountain View was hiking with friends a few years ago, when they stopped to picnic at a rocky desert spot called Little Red Hill near Barstow a few years ago.

McKay cracked open one of the rocks littering the ground all around him, and found clear white inside and a greenish tinge beneath.

At her lab in Mountain View, Janice L. Bishop, a geochemist at the SETI Institute, analyzed the rock to find that the white inside was basically a carbonate mineral called dolomite, with a mix of other carbonates. The carbonates had originally formed in water.

And the greenish tinge underneath the rock was a varied group of living microbe species called Chroococcidiopsis, known as cyanobacteria - blue-green algae.

Bishop analyzed more rocks from the Mojave and found they all held the same mix. The red coating was a form of iron oxide called hematite.

Bishop, McKay and their colleagues published a report in the July 1 issue of the International Journal of Astrobiology.

"We know that the red coating - like all the red rocks on Mars - is iron oxide that acts like a protective coat around the carbonates," McKay said in an interview Tuesday, describing the rock he found. "In the desert, the microbes underneath them need only a little sunlight coming in through cracks in the rocks to live by photosynthesis - it could have been the same on Mars."

Carbonates form in water, but carbonates on Mars have been detected only in several small areas. For example, instruments aboard the Mars rover Spirit, now stuck forever in the sand of Gusev crater, detected carbonates in a rock outcrop named "Pot of Gold" right after it first landed on the planet more than seven years ago. The Mars Reconnaissance Orbiter, aloft above the planet, has also detected carbonates in the rocks of a crater.

Knowing that, Bishop and McKay reason that, just as life lives beneath the red-tinged carbonate rocks in the Mojave, the red rocks on Mars' surface could well hide the evidence of fossil life underneath them.

"Iron oxides coating the rocks are everywhere on Mars," Bishop said. "We've found carbonates that formed in water inside the same desert varnish in the rocks from the Mojave. So they should be broadly distributed on Mars, too."

A spacecraft called the Mars Science Laboratory, a much larger and more powerful rover than either Spirit or its twin, Opportunity, is to be launched in the fall and will start exploring the planet next summer.

"That rover will be able to drill into the rocks when it starts exploring," McKay said.

The Mojave dessert was once a shallow sea some 250 million years ago, and the desert's carbonate rocks formed there. Today's living microbes sheltered beneath the rocks resulted from recent rains.

"We need to be looking for the same thing everywhere on Mars," McKay said. "Only landers - not orbiters - will be able to find them."


E-mail David Perlman at dperlman@sfchronicle.com.

http://sfgate.com/cgi-bin/article.cgi?f=/c/a/2011/07/06/MN3I1K5KK3.DTL

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