Investigation of an ancient Martian meteorite has re-fueled a debate about evidence of possible past life on Mars.
A team of NASA scientists studying the meteorite Y000593, one of a growing number of meteorites chemically identified as having originated on Mars, has reported finding structural and compositional features that may have been formed by biological processes. The tantalizing features include micro-tunnel structures permeating the rock that resemble structures found in Earth basalts modified by the action of bacteria, and microscopic spherules sandwiched between rock layers that contain a richer concentration of carbon than in surrounding layers.
Analysis of Y000593 tells a story of its formation 1.3 billion years ago in a Martian lava flow, and of its forced ejection from Mars 12 million years ago by a major impact event. About 50,000 years ago the tale of this rock's interplanetary voyage ended when it fell onto the Yamato Glacier in Antarctica, where it was discovered by a Japanese research expedition in 2000.
The findings were published in the February issue of Astrobiology, authored by Lauren White of NASA/JPL with co-authors Everett Gibson, Kathie Thomas-Keptra, Simon Clemett and the late David McKay (NASA/Johnson Space Center). In 1996, members of the same team announced that they had discovered features of possible biogenic origin in another Martian meteorite, ALH84001. In both cases the authors are cautious in pointing out that they cannot rule out non-biological processes to account for the features--but in the light of other evidence from robotic missions indicating more Earthly conditions in Mars' past the argument for Martian life is compelling.