<P> For general acceptance of past life in a geologic sample, essentially most or all of these criteria must be met . All seven criteria have not yet been met for any of the Martian samples, but continued investigations are in progress . </P> <P> As of 2010, reexaminations of the biomorphs found in the three Martian meteorites are underway with more advanced analytical instruments than previously available . </P> <P> In 1996, the Martian meteorite ALH84001, a specimen that is much older than the majority of Martian meteorites that have been recovered so far, received considerable attention when a group of NASA scientists led by David S. McKay reported microscopic features and geochemical anomalies that they considered to be best explained by the rock having hosted Martian bacteria in the distant past . Some of these features resembled terrestrial bacteria, aside from their being much smaller than any known form of life . Much controversy arose over this claim, and ultimately all of the evidence McKay's team cited as evidence of life were found to be explainable by non-biological processes . Although the scientific community has largely rejected the claim ALH 84001 contains evidence of ancient Martian life, the controversy associated with it is now seen as a historically significant moment in the development of exobiology . </P> <P> The Nakhla meteorite fell on Earth on June 28, 1911 on the locality of Nakhla, Alexandria, Egypt . </P>

Which of the following is one reason that life could not be sustained in the earliest days on earth