The soil on Mars may contain microbial life, according to a new interpretation of data first collected more than 30 years ago.
The search for life on Mars appeared to hit a dead end in 1976 when Viking landers touched down on the red planet and failed to detect biological activity.
But Joop Houtkooper of the University of Giessen, Germany, said on Friday the spacecraft may in fact have found signs of a weird life form based on hydrogen peroxide on the subfreezing, arid Martian surface.
His analysis of one of the experiments carried out by the Viking spacecraft suggests that 0.1 percent of the Martian soil could be of biological origin. That is roughly comparable to biomass levels found in some Antarctic permafrost, home to a range of hardy bacteria and lichen.
"It is interesting because one part per thousand is not a small amount," Houtkooper said in a telephone interview.
"We will have to find confirmatory evidence and see what kind of microbes these are and whether they are related to terrestrial microbes. It is a possibility that life has been transported from Earth to Mars or vice versa a long time ago."