Page 310 - NS-2 Textbook

ASTRONOMY 305

A closer view of Jupiter from Voyager 1 shows two of its larger moons.

band of liquid-water droplets suspended in the hydrogen-
helium atmosphere, with ice-crystalline, cirrus-like clouds
on top.
Beneath this deep cloud deck, about 125 miles below
the tops of the outermost cloud layer, pressures approach
100 times that of Earth's atmospheric pressure at sea level
(14.6 pOlmds per square inch). The temperature can reach
800 degrees F here.
We do not yet know for sure what is within the cloud
layers. But according to current theory, there is no solid
surface as on the other planets. Instead, the hydrogen is
gradually squeezed into a dense, hot fluid Imder increas-
ing pressure. Finally, about 1,800 miles down, a crushing
gravitational force (equal to 100,000 Earth atmospheres)
and temperatures of 12,000 degrees F change the hydro-
gen and helium into a substance so dense that it behaves
like a liquid. Some 12,000 miles down, under a pressure of
3 to 5 million "atmospheres" and at a tempera hIre of
18,000 degrees F, the hydrogen becomes a metal, in a form
unknown on Earth. Jupiter may also have a core of iron
and other heavy elements, probably no larger than Earth.
While Jupiter's atmosphere is kept constantly churn-
A photo of the 1994 impact of fragments of comet Shoemaker-levy ing by its interior heat, one feature of the planet remains
on Jupiter, taken by the Galilee spacecraft. NASA almost unchanged. That is the mysterious Red Spot in the