Life on Mars? NASA orbiter starts its search.

The orbiter's cameras offer the most detailed images yet of the red planet's surface.

The quest to discover whether Mars ever hosted life is getting a big new boost.

NASA's Mars Reconnaissance Orbiter has begun capturing the most detailed images yet of the red planet. One of the orbiter's cameras has detected a Mars rover – and its shadow. Another of its cameras, whose first images were unveiled Monday, is starting to decipher in unprecedented detail the chemical makeup of minerals on the planet's surface.

The imaging capability is expected to give scientists new insight into whether Mars once might have served as a moist incubator for simple forms of life.

"For understanding big questions like 'In what kinds of environments does life originate?' Mars is still the place to go," says Scott Murchie, lead investigator for the orbiter's mineral-mapping camera, known by its acronym CRISM. The planet and its rocky surface are less exotic and more accessible than other potential targets, such as Jupiter's moon Europa or Saturn's Enceladus. And a decade's worth of missions has uncovered places "where water lingered on the surface, where it ponded," he says. Some of these locations could well have "given life a start" deep in the planet's past.

Monday, Dr. Murchie and his colleagues unveiled the first images from the CRISM, taken last month after the craft reached its operating orbit some 175 miles above the planet. The images focus on one of the youngest and one of the oldest geological formations on the planet.

At the Martian North Pole, CRISM has captured distinct differences in two layers of rock exposed along the steep wall of an ice-draped valley. In the ice cap itself, thought to be less than 200,000 years old, the team is seeing for the first time variations in the contents of dust and ice layers. These results suggest "a complex history of past climate change," Murchie says. Meanwhile, a valley whose rocks are thought to be up to 3.8 billion years old hosts a range of different clays – each bearing a story of the watery environment that gave it its mineral composition. Europe's Mars Express orbiter first spotted the deposits, but the Mars Reconnaissance Orbiter's CRISM has been able to zoom in to detect the types of clays and their distribution down to patches several tens of feet across.

Perhaps the most poignant image, however, comes from the orbiter's HiRISE camera, which can spot objects as small as three feet across. It has captured the rover Opportunity, one of two NASA vehicles operating on the Martian surface, sitting near the edge of a crater. The camera captured not only the coffee-table-size vehicle but also the shadow cast by its spindly mast, which holds a panoramic camera.

The rover's lead scientist, Steven Squyers, noted in his recent book about the project that after spending so much time watching the rovers evolve, it was tough to send them off with no prospect of every seeing them again. "I simply hope someone sees them again," he wrote.

At a briefing highlighting the HiRISE images, Cornell researcher Squyers called the rover picture "one of the most evocative images I've every seen in the history of the planetary exploration program."

Pictures from orbit that can spot such small objects will be indispensable to future rover and lander missions as well as his own, Squyers said. Already his team has started to use HiRISE images to chart Opportunity's course on small jaunts. They plan to use more orbiter images to determine options for traveling around the crater, known as Victoria, and in and out of it.

Opportunity and its sister vehicle Spirit have returned more than 160,000 pictures in nearly three years on the surface. But the images of Victoria crater represent "the most spectacular views of an alien world that human beings have ever seen," says James Bell, one of Squyer's colleagues on the rover project. "I am running out of superlatives to describe the scenery we're seeing,"

Both rovers are operating well beyond their 90-day primary mission. For a planet that has seen more than its share of failed attempts to put landers on it or place orbiters around it, Mars has proved far gentler for the rovers. Mission planners note that, initially, scientists worried that the rovers' batteries would die as the solar panels that charge them grew covered with dust. But breezes have periodically swept the panels clean, giving the batteries the juice they needed to keep the rovers warm and running – especially during two Martian winters.

"You design for worst-case conditions," says John Callas, Mars Exploration Rover project manager at NASA's Jet Propulsion Laboratory. "We've found we have more energy than we needed to survive."

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