Results are in from the first test of Martian soil by the rover Curiosity: So far, there is no definitive evidence that the red planet has the chemical ingredients to support life.
Scientists said Monday a scoop of sandy soil analysed by the rover's chemistry lab contained water and a mix of chemicals, but not the complex carbon-based compounds considered necessary for microbial life.
The latest findings reported at a meeting of the American Geophysical Union meeting in San Francisco came from an instrument aboard the six-wheel rover that baked the soil and analysed the gases released.
Curiosity landed in Gale Crater near the Martian equator in August on a two-year mission to study whether the environment on Mars could have been favourable for life.
The dirt at Curiosity's landing site appeared similar to that found in regions visited by other Mars spacecraft, scientists said.
It contained water, sulfur and possibly perchlorate, a compound made up of oxygen and chlorine.
Nasa's Phoenix lander, which touched down near the Martian arctic, previously found perchlorate in the soil.
The rover did find a simple carbon compound, but scientists have yet to determine whether it's native to the red planet, or came from elsewhere.
Scientists think the best chance of finding complex carbon is at Mount Sharp, a 5km-high mountain rising from the crater floor. Curiosity won't trek there until early next year.
A comment two weeks ago by the mission's chief scientist led to speculation that Curiosity had made a major discovery that would be announced Monday. But Nasa last week said that wasn't the case.
The rover is the most sophisticated spacecraft sent to Mars.
The rover Opportunity has been exploring craters in Mars' southern hemisphere since 2004.
Opportunity's twin, Spirit, fell silent in 2010 after getting stuck in a sand trap.
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