[sci.bio] Jovian atmosphere, Galileo probe

willner@cfa.HARVARD.EDU (Steve Willner) (09/13/89)

From article <25868@iuvax.cs.indiana.edu>, by 
chiaravi@silver.bacs.indiana.edu (Lucius Chiaraviglio):
> 	It has been a long time since I read an article about the composition
> of the Jovian atmosphere, and much (if not all) of what I remember is
> pre-Pioneer and all of it is certainly pre-Voyager.  However, I do remember
> that carbon, nitrogen, oxygen, hydrogen, and sulfur are present in the Jovian
> atmosphere.  I have no data about the amounts of other elements in the Jovian
> atmosphere

One recent paper on Jupiter's atmosphere (Bjoraker et al. 1986, Icarus,
vol. 66, p. 579) discusses ammonia, phosphine (PH3), methane, mono-
deuterated methane, carbon monoxide, and germane (GeH4).  And of
course, most of the atmosphere is hydrogen.  The authors conclude that
N/H, P/H, and Ge/H are near solar abundance at the 5 bar pressure
level.  I would expect most elements to be near solar abundances except
for iron and other dense elements that might be concentrated in the
core.

The outstanding feature of the Jovian atmospheric chemistry is how 
strongly reducing it is.

Incidentally, most of what we know about the constituents of Jupiter's
atmosphere comes from the Kuiper Airborne Observatory.  Spacecraft
missions do measure how density and temperature vary with altitude.
This information is needed to extract quantitative abundances.  And 
for some bodies, the density information has revealed constituents 
(e.g. nitrogen) that are not easily studied with spectroscopy from 
near-Earth platforms.

[discussion of possible life in Jupiter's atmosphere]
> 	It would be nice to find this out before we introduce life there, even
> though the probability of its long-term survival there seems low 

Finding microscopic life forms in Jupiter's atmosphere obviously
involves sending a probe sometime, with a non-zero probability of
contamination.  On the other hand, apparently no effort at all has been
made to sterilize the Galileo probe.

It doesn't seem to me to be possible to sterilize the Galileo probe at
this late date.  The only options I can see are to go ahead as planned
or to cancel the probe portion of the mission.  (Delays for major
modifications would be just as expensive as a new mission.)  Obviously
reasonable people can differ on which is preferable, depending on their
views of (1) the probability of Jovian life, (2) the risk of
contamination, and (3) the value of the data the probe will return.
Since I rate 1 and 2 low and 3 high, I favor going ahead, but others may
reach a different conclusion.
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