QUESTION:
How deep into Jupiter's atmosphere did the probe penetrate?

ANSWER from Dave Atkinson on 20 February, 1996:
First, it is important to keep in mind that although
Jupiter is expected to have a liquid mantle at some depth, this is not really a
liquid surface in the way you might expect.  There is no sitting on a beach and
watching the waves lapping onto the shore on Jupiter!  Although I have been told
that the following is not the best way to think of the interior of Jupiter, my
visualization is as this - the atmosphere gets thicker and thicker with
depth (also getting hotter and hotter). At some point it is so thick that it
really doesn't seem much like a gas, but more like a liquid. As you go deeper
and deeper it begins to seem not so much like a liquid, but more like a solid.
Again, this is probably not exactly true, but it emphasizes the fact that there is no definite boundary between what we might consider the atmosphere, and what
we might consider the liquid interior. 

Galileo reached a depth in the atmosphere of Jupiter of about 140 km below the
one bar level.  If the one bar level is about 71,427 km from the center
(remember that Jupiter is not a sphere, but is oblate - sort of egg shaped, so
the distance from the center of Jupiter to the cloud tops is larger at the
equator than it is at the poles. This is due to Jupiter's fast spin. The
distance from the center of the Planet to the cloud tops at the equator is 
about 71,492 km). You can see that the probe only made it about 2/10 of one 
percent (0.002) towards the center!

Current theories suggest that at a pressure level of 100,000 bars (100,000
times the Earth's surface atmospheric pressure!)  the gaseous ``atmosphere''
slowly  begins to look like a liquid, and deeper still, about 20,000 km below
the cloud tops the liquid Hydrogen should turn into something called liquid
metallic hydrogen.  This is at a pressure greater than 4 millon bars and a
temeperature of about 10,000 degrees Kelvin.  And we are still about 50,000 km
away from the center!  I don't think anyone will go sailing on a Sunday 
afternoon on the oceans of Jupiter!