Search for Past Life on Mars: Possible Relic Biogenic Activity in Martian Meteorite ALH84001

@article{Mckay1996SearchFP,
  title={Search for Past Life on Mars: Possible Relic Biogenic Activity in Martian Meteorite ALH84001},
  author={David S. Mckay and Everett K. Gibson and Kathie Louise Thomas-Keprta and Hojatollah Vali and Christopher S. Romanek and Simon J. Clemett and Xavier D. F. Chillier and Claude Ricketts Maechling and Richard N. Zare},
  journal={Science},
  year={1996},
  volume={273},
  pages={924 - 930}
}
Fresh fracture surfaces of the martian meteorite ALH84001 contain abundant polycyclic aromatic hydrocarbons (PAHs). These fresh fracture surfaces also display carbonate globules. Contamination studies suggest that the PAHs are indigenous to the meteorite. High-resolution scanning and transmission electron microscopy study of surface textures and internal structures of selected carbonate globules show that the globules contain fine-grained, secondary phases of single-domain magnetite and iron… 

Modern terrestrial analogues for the carbonate globules in Martian meteorite ALH84001

TLDR
Modern carbonate globules, located in cracks of submerged volcanic rocks and in calcareous pinnacles in alkaline (sodic) Lake Van, Turkey, appear to be analogues for the ~3.9 billion-year-old carbonates in Martian meteorite ALH84001, indicating that the ALH 84001 carbonates may have formed in similar setting on ancient Mars.

An Evaporation Model for Formation of Carbonates in the ALH84001 Martian Meteorite

Small, discoid globules and networks of magnesium-iron-calcium carbonates occur within impact-produced fracture zones in the ALH84001 Martian meteorite. Because these carbonates contain or are

Alteration Assemblages in Martian Meteorites: Implications for Near-Surface Processes

The SNC (Shergotty-Nakhla-Chassigny) meteorites have recorded interactions between martian crustal fluids and the parent igneous rocks. The resultant secondary minerals — which comprise up to ∼1

Submicron magnetite grains and carbon compounds in Martian meteorite ALH84001: inorganic, abiotic formation by shock and thermal metamorphism.

Purported biogenic features of the ALH84001 Martian meteorite (the carbonate globules, their submicron magnetite grains, and organic matter) have reasonable inorganic origins, and a comprehensive

Origin of carbonate-magnetite-sulfide assemblages in Martian meteorite ALH84001.

  • E. Scott
  • Geology
    Journal of geophysical research
  • 1999
TLDR
It is proposed that carbonates originally formed in ALH84001 from aqueous fluids and were subsequently shock heated and vaporized, suggesting that the ALH 84001 carbonates have a unique origin.

Paleomagnetic Evidence of a Low-Temperature Origin of Carbonate in the Martian Meteorite ALH84001

TLDR
Study of two adjacent pyroxene grains from the crushed zone of ALH84001 shows that each possesses a stable natural remanent magnetization (NRM), implying that Mars had a substantial magnetic field when the grains cooled.

Bulk and stable isotopic compositions of carbonate minerals in Martian meteorite Allan Hills 84001: No proof of high formation temperature

TLDR
The bulk and stable isotopic compositions of the carbonate minerals are open to multiple interpretations and so lend no particular support to a high-temperature origin, and other methods will have to be used to determine the formation temperature of thecarbonates in ALH84001.

Petrographic and geochemical evidence for multiphase formation of carbonates in the Martian orthopyroxenite Allan Hills 84001

Martian meteorites can provide valuable information about past environmental conditions on Mars. Allan Hills 84001 formed more than 4 Gyr ago, and owing to its age and long exposure to the Martian

[Meteoritics and mineralogy on possible ancient Martian life].

TLDR
The mineralogical and biomineralogical evidence for martian bacteria given by McKay et al. (1996) is controversial, and could be formed by non-biogenic processes, so further study of ALH84001 and other martian meteorites is required.
...

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