From Scientific American:
Chemicals in a Martian meteorite that were once held up as possible evidence of life on ancient Mars were more likely the product of heat, water and chemistry, according to a new study. Researchers from the Carnegie Institution of Washington and the University of Oslo in Norway reached that conclusion after comparing the four-pound (two-kilogram) extraterrestrial rock, ALH84001, with samples of earthly volcanic material—and discovering a matching pattern of minerals consistent with a chemical process that yields carbon compounds after rapid heating and cooling.
Although the study does not support the existence of life on Mars, researchers say it shows that some of the chemical precursors of life—at least as we know it—were kicking around on the Red Planet some 4.5 billion years ago.
More here.
