composition of the fluid is unknown, only a temperature range can be estimated but this falls between 0 to 90℃ which would seem entirely appropriate for life processes (7). It was such carbonate veins which were found to host putative microfossils (8).
Irrespective of the existence of features which could be considered to be fossils, carbonate rich portions of martian meteorites tend to have material, more than 1000 ppm, combusting at low temperature i.e. it is an organic form of carbon (9). Unfortunately, this organic matter does not have diagnostic isotopic signature so it can not be unambiguously said to be indigenous to the samples. However, many circumstancial arguments can be made to the effect that it is cogenetic with the carbonate and hence martian. If it could be proved that the organic matter was preterrestrial, then the isotopic fractionation between it and the carbon is in the right sense for a biological origin.
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