The Murchison meteorite - kerogen

Acid and base extractions from this material have been shown to form spontaneous structures in solution termed coercevates that could easily form the basis for protypical membranes (more of this in Chapter 9). Hydrocarbons with chain lengths C15-C30 (both straight and branched chains) and of course PAHs, predominantly pyrene and fluoranthrene, polar hydrocarbons such as aromatic ketones, alkyl and aryl ketones, nitrogen and sulphur heterocycles and most intriguingly purine and pyrimidine analogues have all been observed from this rich carbonaceous cocktail of compounds. Why  

5 Gyr ago. There is evidence that it was reheated as a result of a shock event about 4 Gyr ago and water flowed through it, depositing carbonate globules. It was ejected form the Martian surface by another impact event and orbited the Sun on its own for about 16 million years before intersecting the Earth s orbit and landing some 13000 years ago, impacting into the ice of Antarctica where it was found. 

A very definitive collection of information has been obtained to support the sequence of events just outlined but most striking is the level of confidence and precision in the details. Such was the enthusiasm and imagination regarding the information that during the press conference NASA announced that there was evidence for life on Mars based on data from ALH84001. We will look at some of the details of this extensive and controversial story. 

The anomalous micro-composition of the Martian atmosphere with regard to nitrogen, argon, neon, krypton and xenon has also been compared with trapped gases for the Martian meteorite collection (12 in total). The isotope ratios for 

Amino acid measurements in ALH84001 are almost certainly the result of Antarctic ice contamination. Amino acids are readily soluble in water but PAHs are practically insoluble. Isotopic measurements of 14C show that terrestrial carbon is incorporated into the meteorite during extended stays in the Antarctic ice fields. In addition, microbial activity on the exposed surfaces provides an additional source of biogenic organic material that may be incorporated over time. 

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