The spacecraft is on a mission to look for ingredients in Martian soil and rocks that could support life. But in the first scoop of soil analyzed, there were no definitive signs of the chemical building blocks of life.
Instead, the six-wheel rover detected water and a mix of other chemicals.
The findings were reported Monday at a meeting of the American Geophysical Union meeting in San Francisco.
A comment by mission's chief scientist two weeks ago led to speculation that Curiosity had dug up carbon-based organics, considered an essential ingredient for life.
