Allan Hills 84001: Difference between revisions

* The structures resemble modern terrestrial bacteria and their appendages. Though some are smaller than any present day Earth microbes, others are of the order of 100 - 200 nm in size, within the size limits of [[Nanobacteria|nanobacteria]] and some are up to 1 to 2 microns in diameter.<ref name="impact" />. The smallest ones are too small to contain all the machinery of modern life <ref name="disbelief" />. However, a workshop on the limitations of size of microbes in 1999 found that though modern nanobacteria can't be smaller in volume than the interior of a sphere of diameter 250 ± 50 nm, primitive microorganisms based on a single-polymer system, for instance, RNA based, with [[Ribozymes | ribozymes]] (catalytic RNA) taking the place of [[Ribosomes | ribosomes]] as enzymes for cell replication, could be as small as a sphere 50 nm in diameter. Cells could also shrink after death, or the fossils could be remains of fragments of larger organisms, or they could be pathogens or symbiotes which depend on a host, or they could live in consortia of smaller cells unable to survive independently on their own, or they could be based on biological systems different from the ones we understand. <ref>{{cite book|title=Size Limits of Very Small Microorganisms: Proceedings of a Workshop (1999)|date=1999|url=https://www.nap.edu/read/9638/chapter/2}}</ref>