The Lateral Distribution of Polycyclic Aromatic Hydrocarbons in Allan Hills 84001: Implications for Their Origin

Details The Lateral Distribution of Polycyclic Aromatic Hydrocarbons in Allan Hills 84001: Implications for Their Origin The Lateral Distribution of Polycyclic Aromatic Hydrocarbons in Allan Hills 84001: Implications for Their Origin

Jan 1998

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998mmws.work...50s&link_type=abstract

Workshop on the Issue Martian Meteorites: Where do we Stand and Where are we Going?, p. 50

Biology

2

Carbonates, Microorganisms, Organic Materials, Polycyclic Aromatic Hydrocarbons, Exobiology, Extraterrestrial Life, Snc Meteorites, Microanalysis, Secondary Ion Mass Spectrometry

Scientific paper

Polycyclic aromatic hydrocarbons (PAHs) in ALH 84001 were considered to be evidence for relic biogenic activity on Mars. Crucial for their proposed connection to early life forms is a suggested spatial association with carbonates that contain internal structures resembling terrestrial microfossils. Although each observation can be explained individually a lateral correlation would suggest a genetic link between PAHs and the microstructures. Crucial for the investigation of spatial associations is the lateral resolution of the applied analytical methods. In the mentioned studies, microprobe two-step laser mass spectrometry (microL2MS) was used for the analysis of PAHS. With this technique, an unambiguous determination of a spatial association is limited by its lateral resolution, about 50 micrometers, a size that is comparable with the typical dimension of the carbonate globules. Scanning transmission X-ray microscope (STXM) C mapping and X-ray absorption near-edge structure (XANES) spectroscopic measurements on carbonates from ALH 84001 indicated the presence of organic C (pi-bounded C) within or associated with carbonate globules on the scale of approximately 100 nanometers. A definite identification of the nature of this organic C, which seems to be locally present at percent levels, is not possible with these techniques. Only a small fraction, less than 1 percent of wt, of the organic material in this meteorite may actually be represented by PAHS, and there is isotopic evidence favoring a terrestrial origin for the majority of organic matter in ALH84001

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