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Magnetite morphology and life on Mars
P R Buseck1, R E Dunin-Borkowski, B Devouard
1Department of Geological Sciences, Arizona State University, Tempe, AZ 85287-1404, USA. pbuseck@asu.edu
Summary
Magnetite nanocrystals in a Martian meteorite were thought to indicate past life. However, detailed analysis shows their shapes do not uniquely match those from Earth bacteria, challenging the biological origin theory.
Area of Science:
- Astrobiology
- Mineralogy
- Microbiology
Background:
- Magnetite (Fe(3)O(4)) nanocrystals in Martian meteorite ALH84001 suggest potential extraterrestrial life.
- The biological origin hypothesis is based on morphological and size similarities to terrestrial bacterial magnetites.
Purpose of the Study:
- To precisely define the 3D shapes of magnetite nanocrystals.
- To compare the morphologies of bacterial magnetites with those from the Martian meteorite.
- To evaluate the evidence for a biological origin of Martian magnetites.
Main Methods:
- Transmission electron microscopy utilizing tomographic and holographic techniques.
- Detailed morphological analysis of individual nanocrystals.
- Comparative analysis of crystal shapes from three bacterial strains and meteorite ALH84001.
Main Results:
- Three-dimensional shapes of nanocrystals were successfully defined.
- Distinct morphological differences were observed among nanocrystals from different bacterial strains.
- None of the analyzed bacterial nanocrystal morphologies uniquely matched those from the Martian meteorite.
Conclusions:
- The crystallographic and morphological evidence is insufficient to support a biological origin for the magnetite nanocrystals in ALH84001.
- The inference of former life on Mars based on these minerals is currently unsubstantiated.
- Further research is needed to understand the formation mechanisms of extraterrestrial magnetites.
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