Further, NASA doesn't need a human expedition to Mars to nail down the claim, neuropharmacologist and biologist Joseph Miller, with the University of Southern California Keck School of Medicine, told Discovery News.

"On the basis of what we've done so far, I'd say I'm 99 percent sure there's life there," he added.

 

Miller's confidence stems in part from a new study that re-analyzed results from a life-detection experiment conducted by NASA's Viking Mars robots in 1976.

Researchers crunched raw data collected during runs of the Labeled Release experiment, which looked for signs of microbial metabolism in soil samples scooped up and processed by the two Viking landers. General consensus of scientists has been that the experiment found geological, not biological, activity.