By Ron Cowen, Science News
Tiny fossils discovered on Earth in samples of sulfates, a class of minerals recently found to be common in some parts of Mars, bodes well for finding vestiges of life on the Red Planet, astrobiologists reported April 28 during a briefing held in conjunction with the Astrobiology Science Conference 2010 in League City, Texas.
Bill Schopf of the University of California, Los Angeles, and his colleagues discovered the fossils in deposits of gypsum, or calcium sulfate, that were deposited in the Mediterranean Sea 6 million years ago and then thrust up into the Alps.
The discovery, which included plankton and single-celled organisms such as cyanobacteria (pond scum), some filling areas tens of micrometers in diameter, was a surprise, he said. Schopf and other researchers had assumed that as sulfate crystals grow, they would crush and obliterate any microfossils that might have been trapped inside the minerals, “but that turned out not to be the case,” he said.
Sulfates are known to be abundant in two large areas on Mars — the Meridiani Planum region explored by the Mars rover Opportunity, and Valles Marineris, a vast system of canyons that was recently examined by the European Space Agency’s Mars Express craft.
Because sulfates form in the presence of water, their abundance on Mars had already intrigued researchers looking for signs of past or present life, notes Jack Farmer of Arizona State University in Tempe. The new discovery “gives us great hope that sulfates on Mars might harbor a similar suite of fossils and information on biology,” he said.
It is conceivable that a robotic craft could collect and analyze sulfate samples on the Martian surface. But astrobiologists are also thinking about getting a much more personal look at pieces of the Red Planet.
During the telephone briefing, Mars rover scientist Steve Squyres of Cornell University unveiled a three-stage proposed plan to collect Martian samples and bring them back to Earth. The plan is part of astronomers’ new decadal survey, a blueprint for proposed projects that astronomers submit every 10 years to NASA.
First, a rover would gather samples. Then some time later, another craft would land beside the rover, pick up the material and take it into orbit. Finally, a third ship would rendezvous with the Mars-orbiting craft and bring the material back to Earth.
Dividing the collection and retrieval tasks among three missions spread over a period of several years would reduce the total cost of what would likely be the most complex and expensive robotic mission ever undertaken by NASA, Squyres said. The price tag is a key reason why several other proposed sample-return missions to Mars have never gotten off the ground, he noted.