Going where no Mars rover has gone before

Spacecraft Curiosity to land at Red Planet's Gale Crater

NASA’s six-wheeled Mars rover Curiosity now has a destination on the Red Planet: Gale Crater, an ancient, 150-kilometer-wide depression with a large mountain in the middle. The car-sized robot will spend at least two years wheeling around the rocky basin, collecting information about martian history and looking for signs of habitable environments.

The Mars rover Curiosity will touch down in Gale Crater (above) at the landing site outlined in yellow. This three-dimensional perspective was created using data from NASA’s Mars Odyssey, Global Surveyor, and Reconnaissance orbiters. NASA, JPL-Caltech, ASU, UA

NASA announced the landing site for the $2.5 billion rover on July 22. Scheduled to launch later this year for an August 2012 landing, Curiosity and its payload of instruments will wheel around examining rocks, snapping photos and eating dust. There are 17 cameras on board; one on its belly will capture the probe’s dramatic descent to the surface. A laser will help Curiosity identify intriguing rocks to study; when it finds one, the rover will approach the rock and drill into it, producing a powder that it will then ingest and analyze.

Gale Crater’s central mound is a 5-kilometer-tall stack of sediments that scientists can read like chapters in a history book. The rocky pages will reveal Mars’ geologic and environmental history, including how much water may have drenched the basin once upon a time. The crater also features canyons and fissures that may once have been habitable.

“Our primary goal is to explore habitable environments,” says project scientist John Grotzinger of the Jet Propulsion Laboratory in Pasadena, Calif. “That means we have water present, that means we have a source of energy for microbes to undertake metabolism to live, and that we also have a source of carbon for life as we know it.”

Curiosity will study clay deposits near the base of the mountain, then head toward an area rich in sulfur salts. Both form in the presence of water, says geologist Dawn Sumner of the University of California, Davis.

Gale Crater has been on the short list of Mars target sites for at least a decade, having been mentioned in the early stages of planning for the rovers Spirit and Opportunity. The other finalist for Curiosity’s destination was Eberswalde Crater, potentially a former lakebed and home of an extensive, fossilized river delta. Choosing a landing site was difficult, scientists said, because 60 options initially under consideration were all so good. This time, a group of scientists including astronomer and planetary scientist Jim Bell of Arizona State University led the charge for Gale’s selection. Bell says he didn’t know Gale had been selected until the public announcement. “I thought it could go either way, between Eberswalde and Gale,” he says. “They both have great science potential, and amazing features. So I’m not surprised — but of course I’m delighted.”

According to Bell, Cornell University graduate student Ryan Anderson played a critical role in shaping current understanding of the crater. “It’s both simultaneously wonderful and terrifying that [Curiosity] is going to the landing site I have been studying for the last few years,” Anderson, who is doing fieldwork at a remote site in Canada, wrote on the American Geophysical Union’s website. “Suddenly my work is going to come under very close scrutiny, and I fully expect that [Curiosity] will discover things that completely invalidate some of my interpretations. But … that is what science is about, and I’m thrilled that we will get the answers to some of the big questions about Gale that I couldn’t answer using data from orbit.”

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