NASA's next Mars mission would sniff out 'biosignatures'

• Next-generation rover would grab rock samples that in the future could be returned to Earth
• Two rovers still operating on the Red Planet
• New rover%27s tools would be aimed at detecting past life on Mars

NASA's next Mars rover should recover rock samples for eventual return to Earth, a space agency report recommends, part of an effort to find signs of ancient life on the Red Planet.

The Mars 2020 Science Definition Team report released Tuesday sets out the goals for NASA's next planned rover, set to arrive in the next decade on Mars.

"Had life ever been there and did it leave a mark?" said report chairman Jack Mustard of Brown University in Providence, R.I. "We are looking where life could have once been on Mars."

NASA now operates two rovers on Mars, the nuclear-battery-powered Curiosity rover, a $2.5 billion mobile chemistry lab launched in 2011, and the Opportunity rover, one of two $800 million geology explorers launched in 2003. The Mars 2020 rover would copy the Curiosity rover but carry different instruments, ones aimed at detecting "biosignatures" of past life on Mars, rather than chemistry tools. Instead of the heavy drill used by Curiosity, the new rover would rely on lighter coring-samplers to collect 31 samples for return to Earth.

A still-to-be designed rocket would return the rover's cache of samples to Earth after the 2020 arrival planned for the future rover, according to NASA's John Grunsfeld.

Mars samples analyzed on Earth would be the only feasible way to determine whether rocks truly contained signs of past life on Mars, Mustard said.

NASA's Opportunity rover recently reported evidence of less-sulfurous water during early epochs on Mars billions of years ago, preserved in rock sediments. Curiosity is exploring Gale Crater on Mars, a 96-mile-wide dimple where a mountain is thought to preserve clay layers left from a now-dried crater lake dating to more than 2.5 billion years ago. It also collected signs of flowing water there that was then perhaps drinkable, according to Curiosity mission chief scientist John Grotzinger of Caltech.

The Mars 2020 rover would help NASA take "the next step," in answering the question about whether life existed on Mars, Grunsfeld said.