Nakhlite – Chassignite ( SNC ) meteorites believed to be from the planet Mars . These Martian SNC meteorites would have arrived on Earth though an impact of their own . A massive meteoroid , comet or asteroid would have struck Mars — sending pieces of the Red Planet into space . Eventually some of these Martian space rocks would hit Earth and be found in a number of places on our planet . How do we know these meteorites probably originated from Mars in the first place ? Like a good detective story , scientists look for clues that show a meteorite ’ s possible origin . First , all of these Martian SNC meteorites appear to have come from the same parent Solar System body – an asteroid , the Moon , Mars , etc . Second , Martian SNC meteorites are igneous rock types . Igneous rocks – one of the three major classes of rocks – are formed from the cooling and solidifying of molten material . Martian SNC meteorites and ALH 84001 are of that type of rock , which we would expect to find on Mars . The major clue comes from examination of rocks and soil on Mars itself . In 1976 , the United States landed two probes on Mars . Called the Viking spacecraft , these two unmanned landers conducted a lot of experiments . One of these experiments was to determine specific elements found in the Martian soil . One group of elements , known as the Noble Gases , were found on Mars and closely matched Martian SNC meteorites found here on Earth . This was a major clue : think of fingerprints and how each individual has his or her own set of fingerprints ; no two sets are alike . And these fingerprints basically told scientists “ we ’ re from Mars .” And so based on these clues – same parent body , igneous rocks , and chemical analysis of Mars versus the Martian SNC meteorites – scientists have come to the conclusion that this
Sky ’ s Up
COURTESY OF NASA
This NASA file photo shows the structures in a fragment of the ALH84001 meteorite . These structures have been the source of much controversy since the meteorite ’ s discovery in 1984 .
group of meteorites are indeed from Mars . After ALH 84001 was confirmed as a Martian SNC meteorite , researchers continued to examine the meteorite sample . What they thought they had found next was startling : ALH 84001 appeared to contain microscopic bacteria fossils : proof of life on Mars ! In 1996 , President Bill Clinton and officials from NASA presented the fossilized bacteria evidence in the ALH 84001 Martian SNC meteorite to the American public and the world . Scientists had used a special , very powerful type of microscope , called a scanning electron microscope . It revealed chain-like structures in the meteorite , similar to fossilized bacteria found here on Earth . These structures found within the ALH 84001 Martian SNC meteorite are very similar to those found here on Earth , which are known to be bacteria . The pro-fossilized bacteria scientists believe they might have found similar structures in other Martian meteorites . Not everyone was convinced , however . There was an immediate rejection of the data and theory from other scientists . They claimed the structures found in the ALH 84001 Martian SNC meteorite were geological in nature , not biological . They showed evidence of similar geological structures found in rocks here on Earth . The disagreement as to what these structures are continues today , with both groups presenting data that supports their claims . So will we ever resolve the mystery of the ALH 84001 Martian SNC meteorite ? Probably eventually , especially when we bring rock samples back from Mars to study here on Earth . Even then it might take years – even decades – to determine the truth about the ALH 84001 Martian SNC meteorite structures . Yet that ’ s part of the adventure of science — working with the unknowns and making discoveries . o o o In addition to being a longtime STEM advocate , Dr . Mike Reynolds is a dean and professor of astronomy and physics at Florida State College and a recognized expert on meteoritics . He participated in NASA ’ s Teachers in Space Program and has served as executive director of the Chabot Space & Science Center .
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