Jupiter is a giant gas planet which is made up of about 90% hydrogen and
10% helium. Jupiter was first visited by the Pioneer 10 spacecraft in 1973.
It was later visited by Pioneer 11, Voyager 1, Voyager 2 and Ulysses. The
spacecraft Galileo is currently in orbit around Jupiter and will be
sending back data for at least the next two years.  Jupiter is so big
that you could cram 1,000 Earths inside of it! That's *mighty big*!
It is thought that Jupiter's "Great Red Spot" is a storm of swirling
gas that has lasted for hundreds of years. Scientists are still unsure as
to how such a storm could last for so long. Jupiter has 16
known moons! There are four large "Galilean" moons, and 12 small ones.


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