While NASA’s next Mars rover scours for signs of habitable environments, it will deposit small pebbles and soil samples into a special cache for a possible return to Earth.

Possible Destination

Mawrth Vallis

Terby Crater

Buoyed by NASA’s new science chief Alan Stern, the agency is laying the groundwork for a sample return mission in 2020, said John Grant, co-chairman of the committee working to choose the landing site for the Mars Science Laboratory, or MSL.

Some scientists believe that a sample return mission will be the best way to definitively prove if life ever developed on another planet.

"You look around and can’t help but think that life here is unique and special. If you find life elsewhere, that tells you that conditions that existed here…existed somewhere else and that biologically, we’re not unique. Philosophically, that has a lot of implications," Grant said in an interview with Discovery News.

"If you’ve got another planet with life right here in the solar system .. and there are a lot of candidates — Mars, Europa, Ganymede — life could be commonplace. It may not be rare or unique," Grant said.

After an initial pot-luck attempt to find life with the Viking missions of the 1970s, NASA embarked on a strategy of following Mars’ past water in hopes of finding the best places to search for life.

Mars Science Laboratory, which is scheduled for launch in 2009, is the agency’s boldest attempt to hone in on a potential habitat. Scientists last week narrowed a list of 50 candidate landing sites for MSL to their top six picks.

A series of focused observations with orbiters now circling Mars will be conducted to further assess the sites for accessibility and scientific potential, said planetary geologist Matt Golombek, with NASA’s Jet Propulsion Laboratory and the MSL landing site committee co-chair.

Scientists decided not to return to the rover Opportunity’s landing site in the equatorial region of Mars which shows evidence of a shallow salty sea. Instead, the consensus of the 150 workshop participants — more than twice the number expected to attend — was to explore a region that has clays, which are believed to have formed by water interacting with rocks.

"All are potentially habitable environments," Golombek told Discovery News. "That’s the point of the mission."

Some of the sites show distinctive fan-shaped structures believed to be body prints of standing water. Others show actually clay deposits on the surface. A few have both.

"On Earth, there is a strong relationship between clay-bearing minerals and places that can sequester and even promote life," Golombek said.

Most of the the sites will require MSL to drive for several weeks if not months from where it lands to reach the most scientifically interesting features, Golombek said. But with the rover designed to operate for a full Martian year — or about 687 Earth days — scientists believe the driving time is worth it.

Scientists will have to narrow the landing site options to either the four more northern locations — Nili Fossae Trough, Marwth Vallis, and Runcorn and Jezero craters — or the two southern ones — Holden and Terby craters — next year.

Wherever MSL travels, bits of interesting materials will be picked up and deposited into a wire mesh basket about the size of a hockey puck, Golombek said.

If and when NASA approves a sample return mission, the cache will be ready and waiting.

Via: Discovery Channel