More building blocks of life found on Mars

WASHINGTON - A NASA rover has detected a bonanza of organic compounds on the surface of Mars and seasonal fluctuations of atmospheric methane in findings released on Thursday that mark some of the strongest evidence ever that Earth's neighbor may have harbored life.

But NASA scientists emphasized there could be nonbiological explanations for both discoveries made by the Curiosity rover at a site called Gale Crater, leaving the issue of Martian life a tantalizing but unanswered question.

Three different types of organic molecules were discovered when the rover dug just 5 centimeters into roughly 3.5 billion-year-old mudstone, a fine-grained sedimentary rock, at Gale Crater, apparently the site of a large lake when ancient Mars was warmer and wetter than the desolate planet it is today.