ALH84001 A Meteorite From Mars

Introduction The analysis of meteorites that have landed on Earth has given scientists an improved understanding of the makeup of our solar system. The analysis of meteorites that have landed on Earth has given scientists an improved understanding of the makeup of our solar system. Using this information has allowed scientists to piece together a more accurate history of our solar system over its 4.6 billion year lifetime. Using this information has allowed scientists to piece together a more accurate history of our solar system over its 4.6 billion year lifetime. Approximately 24,000 meteorites have been discovered and cataloged on Earth. Remarkably, 34 of these have been identified as coming from Mars. Approximately 24,000 meteorites have been discovered and cataloged on Earth. Remarkably, 34 of these have been identified as coming from Mars.

Allan Hills - Antarctica

ALH84001 On December 27, 1984, while out searching for meteorites on snowmobiles, members of ANSMET (Antarctic Search for Meteorites) found an unusually-looking 1.9- kilogram meteorite which was given the label of Alan Hills or ALH84001 for short. On December 27, 1984, while out searching for meteorites on snowmobiles, members of ANSMET (Antarctic Search for Meteorites) found an unusually-looking 1.9- kilogram meteorite which was given the label of Alan Hills or ALH84001 for short. In 1993, ALH84001 was identified as a meteorite that had come from Mars. In 1993, ALH84001 was identified as a meteorite that had come from Mars. On August 7, 1996, geochemist David McKay and eight co-authors presented the stunning conclusion that they had found evidence of past evidence of past life on Mars in ALH On August 7, 1996, geochemist David McKay and eight co-authors presented the stunning conclusion that they had found evidence of past evidence of past life on Mars in ALH84001.

Key Events of ALH billion years ago Solidified from molten state on Mars billion years ago Lifted to Mars’ surface by a blast 3.6 – 1.4 billion years ago Minerals deposited in cracks 16 million years ago Blasted off the surface of Mars into space 13,000 years ago Lands in Antarctica 28 years ago Discovered by ANSMET team

Evidence For Life Carbonate globules – similar to bio- minerals found on Earth Carbonate globules – similar to bio- minerals found on Earth Magnetite ( Fe 3 O 4 ) and iron sulfide – similar to magnetobacteria Magnetite ( Fe 3 O 4 ) and iron sulfide – similar to magnetobacteria Polycyclic aromatic hydrocarbons (PAHs) – associated with decaying organisms Polycyclic aromatic hydrocarbons (PAHs) – associated with decaying organisms Microstructures – nanobacteria or appendages of larger bacteria Microstructures – nanobacteria or appendages of larger bacteria

Alternate Explanations Experiments show microorganisms are not needed to form carbonates Experiments show microorganisms are not needed to form carbonates Similar magnetite has been made inorganically in the lab Similar magnetite has been made inorganically in the lab 80 % of the PAHs come from terrestrial contamination. PAHs of similar isotopic composition have been found in carbonaceous chondrites. Evidence of organic material does not prove life. 80 % of the PAHs come from terrestrial contamination. PAHs of similar isotopic composition have been found in carbonaceous chondrites. Evidence of organic material does not prove life. No known life is as small as the structures found in ALH84001 No known life is as small as the structures found in ALH84001

Conclusions Some of the organic material found in ALH84001 probably did originate on Mars Some of the organic material found in ALH84001 probably did originate on Mars It is difficult to differentiate between organic material and biological material It is difficult to differentiate between organic material and biological material All of the evidence in ALH84001 has been reproduced inorganically in the lab All of the evidence in ALH84001 has been reproduced inorganically in the lab NET: Extraordinary claims require extraordinary evidence. Most scientists are not convinced that ALH84001 presents evidence for life on Mars.