Scientists see Mars in a new light

CHICAGO – As NASA’s twin robotic rovers arrived on Mars one year ago, the planet looked to many scientists like a vast, inert museum where water and warmth gave way long ago to a cold and seemingly dead world.

That picture has shifted, experts say, thanks to findings from the rovers and other research that suggest Mars remains a geologically dynamic planet with tantalizing hints of life.

The new Mars is an untamed place with possibly active volcanoes and geothermal springs, dry sea beds, recent glacier activity and traces of methane in its atmosphere. That last fact may prove the most intriguing, scientists say, because the mysterious methane could be coming from living Martian microbes.

At the forefront are rovers Opportunity and Spirit, still charting new ground one year after landing on opposite sides of the planet. Last March, Opportunity found bedrock containing the first tangible evidence that Mars once had shallow, salty seas – a discovery Science magazine dubbed its “Breakthrough of the Year.”

Evidence for recent glaciers and volcanic activity, published Dec. 23 in the journal Nature, came from the European probe Mars Express, which has photographed huge swaths of the Martian surface. The orbiter found relatively young lava flows in the craters of several Martian volcanoes, including Olympus Mons, the biggest volcano in the solar system at 15 miles high.

Scientists analyzing the Mars Express photos found a few meteor-impact craters in several of the lava fields – a sign the features formed within the last 2 million years or so.

Microbes such as bacteria are just one possible explanation for the methane, detected this year by three teams using space-based and earth-based instruments. Other possible sources include geothermal vents, hydrogen reactions or natural gas akin to deposits on Earth, which stem from ancient material.

If life survives on Mars today, Opportunity’s observations may give hints of the habitats where it can be found. The bedrock sediments in the small crater where Opportunity came to rest formed in shallow water that was salty and about as acidic as tomato juice, experts believe.

Many experts say signs of recent volcanic activity make it plausible Mars still has geothermal springs. Although the upwelling water might not last long on the surface, such spots would be natural places to look for microscopic organisms such as bacteria.