allan hills 84001 allan hills 84001 allan hills 84001 (alh84001) is a fragment of a martian meteorite that was found in the allan hills in antarctica on december 27, 1984, by a team of american meteorite hunters from the ansmet project. like other members of the shergottite–nakhlite–chassignite (snc) group of meteorites, alh84001 is thought to have originated on mars. however, it does not fit into any of the previously discovered snc groups. its mass upon discovery was 1.93 kilograms (4.3 lb). allan hills 84001 meteorite fragment alh84001typeachondriteclanmartian meteoritegroupletorthopyroxenitecompositionlow-ca orthopyroxene, chromite, maskelynite, fe-rich carbonateshock stagebweathering gradea/bcountryantarcticaregionallan hills, far western icefieldcoordinates76°55′13″s 156°46′25″eobserved fallnofound date1984tkw1930.9 g related media on wikimedia commons in 1996, a group of scientists found features in the likeness of microscopic fossils of bacteria in the meteorite, suggesting that these organisms also originated on mars. the claims immediately made headlines worldwide, culminating in then-u.s. president bill clinton giving a speech about the potential discovery. these claims were controversial from the beginning, and the wider scientific community ultimately rejected the hypothesis once all the unusual features in the meteorite had been explained without requiring life to be present. despite there being no convincing evidence of martian life, the initial paper and the enormous scientific and public attention caused by it are considered turning points in the history of the developing science of astrobiology. history and description alh84001 on display at the smithsonian museum of natural history alh 84001 was found on the allan hills far western icefield during the 1984–85 season, by roberta score, lab manager of the antarctic meteorite laboratory at the johnson space center. alh84001 is thought to be one of the oldest martian meteorites, proposed to have crystallized from molten rock 4.091 billion years ago. chemical analysis suggests that it originated on mars when there was liquid water on the planet's surface. in september 2005, vicky hamilton, of the university of hawaii at manoa, presented an analysis of the origin of alh84001 using data from the mars global surveyor and 2001 mars odyssey spacecraft orbiting mars. according to the analysis, eos chasma in the valles marineris canyon appears to be the source of the meteorite. the analysis was not conclusive, partly because it was limited to areas of mars not obscured by dust. the theory holds that alh84001 was blasted away from the surface of mars by the impact of a meteor about 17 million years ago, and fell on earth about 13,000 years ago. these dates were established by a variety of radiometric dating techniques, including samarium–neodymium (sm–nd), rubidium–strontium (rb–sr), potassium–argon (k–ar), and carbon-14 dating. other meteorites that have potential biological markings have generated less interest because they do not contain rock from a "wet" mars; alh84001 is the only meteorite originating when mars may have had liquid surface water. in october 2011, it was reported that isotopic analysis indicated that the carbonates in alh84001 were precipitated at a temperature of 18 °c (64 °f) with water and carbon dioxide from the martian atmosphere. the carbonate carbon and oxygen isotope ratios imply deposition of the carbonates from a gradually evaporating subsurface water body, probably a shallow aquifer meters or tens of meters below the surface. in april 2020, researchers reported discovering nitrogen-bearing organics in allan hills 84001. a later study in 2022 concluded that alh84001 did not contain martian life; the discovered organic molecules were found to be associated with abiotic processes (i.e., "serpentinization and carbonation reactions that occurred during the aqueous alteration of basalt rock by hydrothermal fluids") produced on the very early mars 4 billion years ago instead. hypothetical biogenic features