[sci.astro] Possible Life on Venus: A Question

chiaravi@silver.bacs.indiana.edu (Lucius Chiaraviglio) (04/10/89)

In article <kYDtAmy00Xoe43iElp@andrew.cmu.edu> jd3l+@andrew.cmu.edu
(Jean-Marc Debaud) writes:
>There is a question that has been distrubing me lately,
>
>We discover not a long ago living "parasites" that are
>very close to paramecia organism very deep in the
>Atlantique Ocean. What is surprising is the capacity of
>those organism to live and reproduce in very hot water
>located near permanent volcanic activities.

	Are you sure that these organisms are similar to paramecia?  I have
heard of archaebacteria living in very hot water, but no eukaryotes.  At any
rate, if they are free-living, they are not parasites.

>According to common knowledge (I am a logician not
>a biologist) I thougth that proteins as well as DNA chains
>could not be replicated and therefore not formed under high
>temperature.

	Certain proteins are stable at quite high temperatures (80`C is not
uncommon), and using various measures an organism can stabilize its proteins
and DNA.  Such measures include maintaining very high internal salt
concentrations and other means of ensuring that the ratio of water to
everything else is small (but nonzero).

>Furthermore, my understanding was that the reasons above
>(temperature, pressure) were the motive why scientist could
>not beleive of forms of life on Venus. So do we have to scrap
>this belief and restart again ?
>
>Or am I missing anything here ?

	One requirement of terrestrial life is that the water within it be
liquid, whatever the temperature and pressure.  Things have been found that
can grow at 135`C, and certain archaebacteria have successfully been cultured
in the laboratory at 112`C.  However, all of these organisms must be kept
under enough pressure to keep them from boiling when they are grown at those
temperatures.  Such pressures are found at the bottom of our oceans.  However,
at temperatures over the critical point of water, such as those found on
Venus, no amount of pressure will keep the water liquid.  Therefore, life with
a terrestrial biochemistry will not be able to exist on Venus.  Of course,
this does not rule out some form of life with a totally different kind of
biochemistry.

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