Expert: Tom Whiting - 1/26/2010

Question
Why isn't Jupiter habitable?

Answer
Hi Elaine,
By definition, Jupiter is one of 4 gas giants in the Solar System, the others being
Saturn, Uranus, and Neptune.  This means that there is no hard, rocky surface as we find
on the "terrestrial-type" planets of Mercury, Venus, Earth, and Mars... where one can properly
walk around (with the proper spacesuit protection) if they wish to.
There is no surface as we know it, on a gas giant, being made almost completely of a big
ball of gas... hydrogen, helium, methane CH4 and Ammonia NH3...with trace amounts of other
gases.  (Doesn't make for very good breathing either, plus no liquid water, plus extremely cold,
like -200 degrees or colder).
Even IF there was a hard surface under the thick atmosphere, a standard 200 pound human would weigh almost 500 pounds, literally almost locked onto the "surface" if it existed.  Plus the
amount of energy...fuel, to escape from the high gravitational well, would be enormous, compared
to our Earth's standards of launching rockets.
Therefore, no one will ever "go" to Jupiter, but we WILL eventually visit the moons of Jupiter,
as we could walk on those as they do have a surface.  (Assuming the radiation isn't too high).
And their escape velocity is a lot less.

All gas giant planets are just "failed" stars.  Jupiter came very close (within a few million
years - a very short time astronomically) of becoming a little red dwarf star, but our sun
ruined that scenerio by triggering off nuclear fusion some 4.6 billion years ago, blowing out all
the dust and gas, most of it, out from the Solar System, effectively stopping the large quantity accretion phase of the planets (including the Earth)....so whatever you have, that is it!  And you ain't accreting any more mass.  Except for an occasional comet or asteroid impact.   But that's another story.
Hope this helps,
Clear Skies,
Tom Whiting
Erie, PA