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Antarctica is also important in the search for life on Mars because it is where the most famous of the Martian meteorites - ALH84001 - was discovered. Asteroids and comets that have slammed into Mars in the past have sent pieces of the planet into space and some of these pieces have come to Earth as meteorites.

In 1996, David S. McKay and colleagues demonstrated organic compounds in ALH84001 and some other Mars meteorites suggesting that the Viking GCMS data are, in fact, not reliable. McKay and his team have also identified what may be tiny fossils in the rock remaining from bacteria-like organisms although other researchers disagree that these are Martian fossils. Some of the investigators who contest the conclusions of the McKay group are concerned that the possible fossils in ALH84001 may be from terrestrial microbes while others believe that they may not be fossils at all but the result of non-biological processes. Scientists are also debating whether the structures identified in the meteorite, which average 100 nm in size, are large enough to have contained all that would be needed to carry out the minimum functions necessary for independent lifeforms. These issues have not yet been resolved and research and debate continues.

Some of the other Martian meteorites that are being studied for possible evidence of past Martian life include one that landed in Nakhla, Egypt in 1911.