Life on Venus.......
dmr at nhm.ac.uk
Wed Feb 14 04:05:52 EST 1996
>You are right on this point. Cyanobacteria are unique among prokaryotes
>in that they have photsystem II, which creates oxygen. I have never
>heard anyone suggest that cyanobacteria were the first forms of life.
I didn't say they were the first form of cellular life but that the
earliest fossils were cyanobacteria-like. If you form chains of cells with
some slightly larger (heterocysts??) and you build stromatolite-like
structures, then it is a reasonable guess that the organisms were
The main point is that you have something like this at 3500 My. It doesn't
evolve overnight so the origin of life must have been very much earlier,
but you have the massive-impact events at about 4000 My which are believed
to have evaporated the oceans. The hot vent origin theory is very
difficult because nucleic acids have a very short half-life at high
temperatures and hyerthermophiles have evolved mechanisms to protect their
nucleic acids from thermal damage. There is a good deal of literature out
there on this subject.
Dr D.McL. Roberts, Tel: +44 171 938 8790
Dept. Zoology, Fax: +44 171 938 9158
The Natural History Museum,
London SW7 5BD
Great Britain Email: dmr at nhm.ac.uk
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