It's dirt, but not as we know it: Curiosity analysis flattens hopes of a Mars-shaking discovery

Picture of Mars from the Curiosity rover (Getty Images)

The Curiosity Mars rover has discovered something interesting in a scoop of ruddy sand, but Nasa scientists say they're not quite sure what it means.

Sand that was shake-and-baked inside the car-size rover's chemistry kit bubbled off traces of organic compounds, mission scientists said at a news briefing Monday at the annual meeting of the American Geophysical Union.

Such compounds, made of carbon and chlorine, are of the type that, in some cases, indicate microbes in the soil.

But such compounds also could be contamination from the rover itself — or they may have rained onto the surface inside meteorites, said Paul Mahaffy, a mission scientist from NASA's Goddard Space Flight Center in Greenbelt, Md.

"It's unclear if the carbon is Martian or terrestrial," Mahaffy said.

Further tests will help clarify the source of the chemicals, but mission scientists cautioned that the rover is not equipped to find life itself, only the conditions that may be ripe for life.

If they rule out contamination, the science team will "get into the complex question of whether this is some type of biological material," said project scientist John Grotzinger. "That's well down the line for us."

Jim Bell, president of the Planetary Society, who is not involved in the mission, said searching for life on another planet is difficult. "It's hard to find [microbial] life here on Earth, which is teeming with it. You've got to take samples back to high-tech labs."

Curiosity's middle name, Grotzinger said, is patience. "There's not going to be one single . . . hallelujah moment."

The minor announcement from the Mars Science Laboratory team comes as a letdown after weeks of speculation that the rover had made an "earthshaking" discovery, as reported by NPR last month.

That radio story, Grotzinger said, sprang from a misunderstanding.

A reporter happened to be sitting with him as the rover's most sophisticated instrument, called the SAM, beamed back data showing it was working as designed. The science team started "hootin' and hollerin'," Grotzinger said.

His lesson: Be careful what you say.

The Curiosity mission was designed to find conditions on Mars conducive to life: water, heat and organic compounds: the building blocks of life on Earth.

Three months after a dramatic touchdown and nearly flawless operations, the mission has ticked off one of those boxes: It landed in a dry riverbed, evidenced by rocks shaped by flowing water.

The rover has also beamed 11,000 pictures back to Earth and taken millions of readings of the planet's weather and radiation levels. Next up: testing the rover's drill on a rock.

"We hope to start that before the holidays," Grotzinger said.