Mapping Mars for signs of life

The ruddy surface of the alien world unravelled before Ken Edgett's eyes in noodle-like strips. Each image from the camera aboard the Mars Global Surveyor covered a 2-mile-wide swath of dunes, rock valleys and jagged ribbons of dry ice. Twelve orbits a day, for eight years with a total of 243,926 pictures of the Martian wasteland.

Edgett, a bushy-haired, 6-foot-2 scientist, stared himself half-blind as he scanned the pictures from his office in an industrial park outside San Diego. His companion through the years of surveying the planet was Mike Malin, the designer of the spacecraft camera and the president of Malin Space Science Systems.

Together, they have studied more Martian craters, rock fields and mountains than any earthling. You might call them the Lewis and Clark of Mars. Just as the American adventurers explored west of the Mississippi, Malin and Edgett have taken a journey across Mars. But instead, they hitched a ride on a spacecraft.

Edgett has come to know Mars so well that you can show him a picture of a spot on the Red Planet and he can give you a good idea of where it is.

The two are an unusual pair. Edgett, 41, gregarious, who loves slapstick movies once ate an animal's foot in a futile attempt to win tickets to a Pink Floyd concert.

Malin, 57, smaller and more reticent, is a MacArthur Foundation "genius" award winner and a former university professor.

"Collectively they do some of the most meticulous science that I've seen," said Robert Pappalardo, a planetary expert at the Jet Propulsion Laboratory (JPL) in La Canada Flintridge, California.

Mars is no longer a dead rock. Edgett and Malin have detailed a rich and complex world that might include the existence of some form of life.

"Besides Earth, Mars is once again the most exciting place in the solar system," said Bruce Murray, an astronomer at the California Institute of Technology.

Malin, true to form, is unimpressed with the implications of his own work.

"I don't actually think there is life on Mars," he said. For Edgett, Mars had been a fascinating place since he was growing up in Rochester, New York.

Malin had been exploring the cosmos since he was a graduate student in the 1970s at Caltech, studying planetary sciences. Later, at JPL and Arizona State University, where he was a geology professor, he embraced photo-geology — the study of geology through high-resolution imagery.

In 1990, Malin tossed away his promising academic career to start a company building cameras for Nasa.

Preserved records

Malin's gamble nearly failed when the first camera his team built was lost with the Mars Observer spacecraft in 1993. He was lucky to have parts left over for a second camera when the Mars Global Surveyor mission came around four years later.

It took nearly a year for Global Surveyor to reach Mars. Malin and Edgett, who had joined the company anxiously waited through the journey.

Just weeks before its arrival, another craft, Mars Pathfinder dropped a little robot onto the surface. The Sojourner rover was a hit with the public, rolling around its landing site and taking pictures of rocks.

Global Surveyor finally eased into its 234-mile-high polar orbit. In September 1997, the first close-up images began appearing on Malin's computer. "This is a completely different Mars than anyone was thinking about," Caltech's Murray said.

The first big surprise was the great quantity of layered rocks, especially in Valles Marineris, the six-mile-deep cavity that rips 3,000 miles across the Martian surface.

"Earth didn't preserve those rock formations," Edgett said, referring to the layered rocks. "Mars is the only terrestrial planet with an atmosphere that has preserved a record of its earliest history." On any given day, Edgett reviewed 50 to 300 pictures.

Hints of water

Most days, Malin stopped by Edgett's office for a chat. "Often, out of those discussions came new discoveries," Edgett said. Edgett was fascinated by textures in the landscape. Around Alba Patera, a volcano, the surface had a "bubbly" appearance. The equatorial region was sandy.

In Noachis Terra in the south, there were huge dunes. But these dunes were different from Earth's. Channels cut across their surfaces.

He wasn't sure what he was looking for, but his goal was clear — to find some sign of water flow. In 1999, Edgett spotted narrow gullies along a canyon wall. They were at most a few thousand years old.

It could be an indication of water erosion. He decided to focus in on the gullies whenever Global Surveyor passed overhead to look for any changes.

Then in 2005, he saw something unusual. Shiny, white ice-like flows appeared in two of the gullies. The flows were near the limits of the camera's resolving powers. He and Malin accounted for the time of day, the strength of the Sun and every possible counter-explanation they could find.

They held on to their discovery for a year while they tested the theory and wrote it up for publication in the journal Science.

In December, Edgett and Malin announced their discovery, which was quickly hailed as one of the greatest solar system finds in decades.

"Now thinking about life on Mars isn't a search for past life," said Pappalardo of JPL.