Mars mission will probe Red Planet’s past, present

By Nadia Drake

Web edition: August 1, 2012

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NASA’s rover Curiosity is aiming to land on August 5 in Gale Crater, an enormous impact basin with a large mountain in the middle. There, Curiosity will search for signs of life-friendly environments — past or present — and attempt to assemble an environmental history of the Red Planet.

Credit: NASA, JPL-Caltech, ESA, DLR, FU Berlin, MSSS

Editor’s note: This is the second of two articles previewing the Mars Curiosity rover’s upcoming Mars landing. (See also "Curiosity readies for dramatic entrance.") The vehicle is scheduled to land on Sunday evening, August 5, Pacific Daylight Time. Science News astronomy writer Nadia Drake will cover the landing live from NASA’s Jet Propulsion Laboratory in Pasadena, Calif.

If, late in the evening of August 5, NASA’s Curiosity rover survives what might be the most daring interplanetary touchdown in history, the six-wheeled robot will find itself in a dramatic landscape ripe with research opportunities: Gale Crater, an enormous basin with a 5-kilometer-tall mountain in the middle, called Mount Sharp. There, Curiosity will look for evidence of water, energy sources and organic carbon — the hallmarks of life-friendly environments, past or present.

By reading the rocky clues hidden in that mountain, the rover will also try to peer back in time and learn what environments on ancient Mars were like. For 98 weeks — one Mars year — the rover and its 75 kilograms of science instruments will attempt to probe the deep Martian past.

Though the mountain is the mission’s primary target, scientists hope the rover will first alight on one particularly intriguing patch of rock.

“We don’t really know what that material is,” says project scientist John Grotzinger of Caltech.

Unlike the rest of the crater floor, this rock appears to be hard and capable of holding onto the heat of the day. In the absence of volcanic activity, that property is suggestive of compounds cemented together by water. Since scientists are interested in studying where water flowed on ancient Mars, the warm, rocky patch would be an ideal place for the rover to start poking around.

But not for too long. Mount Sharp is “going to be there on the horizon, calling to us,” says Ryan Anderson of the U.S. Geological Survey Astrogeology Science Center in Flagstaff, Ariz.

The ancient pile of sediments, rising higher above the surrounding terrain than any mountain in the Lower 48, holds in it the rocky clues to understanding ancient Martian environments and past habitability. The evidence takes the form of mineral layers, some of which — like the clays near the mountain’s base — require water to form. As the rover climbs Mount Sharp, the clues it deciphers will help scientists understand how a planet that was once more like Earth became the dry, dusty and acidic ball it is today. “Suddenly, the planet seems to have gotten dry,” Grotzinger says. “I like to call it the great desiccation event.”

The rover will analyze rocks with a variety of instruments. One, the ChemCam, uses a laser to vaporize a small sample of rock or soil from up to seven meters away. Then, scientists can study the ingredients. Another instrument will drill into rocks, creating a powder that the rover can ingest and analyze for signs of things like organic carbon — a job that Grotzinger says is probably the most difficult the rover will encounter. “This is a really hard thing to do, even on Earth,” he says. “Even on a planet that’s teeming with life, [organic carbon] almost never gets preserved.”

Comparing Mars and Earth may help scientists understand how environmental triggers influence the evolution of life. When studying life’s origins and diversity on Earth, Grotzinger says, scientists often wonder what would have happened if specific events — such as the flooding of Earth’s atmosphere with oxygen about 2.4 billion years ago — hadn’t occurred. “Is there some place that you can compare to where that didn’t happen?’ That’s Mars,” he says.