“In this study, we interpret our results to suggest that the in situ inorganic hypotheses are inconsistent with the data, and thus infer that the biogenic hypothesis is still a viable explanation,” said lead author Thomas-Keprta, senior scientist for Barrios Technology at JSC.
“We believe that the biogenic hypothesis is stronger now than when we first proposed it 13 years ago,” said Gibson, NASA senior scientist.
In addition to the new paper on ALH84001, the JSC team has published a paper that identifies shapes or morphologies in Martian meteorites that resemble known microfossil and microbial shapes in samples from Earth. These new shapes, seen with a scanning electron microscope, are termed biomorphs because of their close resemblance to known, biologically produced features on Earth. The biomorphs observed in the meteorites will be the focus of the JSC team with more detailed studies, including chemical and isotopic analyses.
“The evidence supporting the possibility of past life on Mars has been slowly building up during the past decade,” said McKay, NASA chief scientist for exploration and astrobiology, JSC. “This evidence includes signs of past surface water including remains of rivers, lakes and possibly oceans, signs of current water near or at the surface, water-derived deposits of clay minerals and carbonates in old terrain, and the recent release of methane into the Martian atmosphere, a finding that may have several explanations, including the presence of microbial life, the main source of methane on Earth."