Jupiter is the fifth planet from the sun, and the largest planet in the solar system. Jupiter is so large that it is more than two times the size of all of the planet's masses combined. Jupiter is a gas giant being mostly made of gases. Jupiter is composed of hydrogen, helium, methane, and ammonia. a day on Jupiter is shorter than a day on any planet, one day on Jupiter is 9 hours and 55 minutes. However, Jupiter's year is much longer than earth's. A year on Jupiter lasts about 11.9 earth years. Jupiter has a great red spot that is a constant storm on Jupiter. The great red spot on Jupiter is so big that two earth's could fit side by side in it. There are 64 moons orbiting Jupiter, four of which can be easily seen through a small telescope. One of Jupiter's moons, Ganymede, is the largest moon in the solar system.