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From Earth to Pluto: A Digital Time Capsule for the World of Tomorrow
  

Space Topics

Jupiter


Truly the king of the planets, Jupiter is more massive than all of the other planets in the solar system combined, plus their satellites, the asteroids, and all the comets! A mini solar system unto itself, Jupiter is attended by four of the biggest moons in the solar system, the Galilean satellites Io, Europa, Ganymede, and Callisto, all of which are larger than Pluto, plus a veritable swarm of other tiny moonlets.

Known as a "gas giant," Jupiter's deep gaseous atmosphere merges imperceptibly into a layer of liquid hydrogen. Within the planet pressure and temperature are so high that there is no clear boundary between the gas and liquid. The atmosphere is composed primarily of hydrogen and helium in nearly the same abundances found in the Sun and other stars. This enormous planet rotates faster than any other in the solar system, so fast that its shape is noticeably flattened out of a sphere. The banded and colorful atmosphere contains many gigantic oval-shaped storms. One of these, the Great Red Spot, is larger than two Earths and has persisted in Jupiter's atmosphere at least since the 1700s.

Jupiter was the first target for Pioneers 10 and 11 in 1972 and 1973 and Voyagers 1 and 2 in 1979. From 1995 to 2003, the Galileo orbiter toured the Jupiter system. Jupiter's mass makes it an attractive waypoint for gravity assist trajectories, which allow spacecraft to reach otherwise inaccessible points in the solar system. The solar orbiter Ulysses in 1992 and Saturn orbiter Cassini in 2000 took advantage of Jupiter gravity assists. The Pluto mission New Horizons will be the next spacecraft to fly by Jupiter in February 2007.

Jupiter Numbers
Size: largest planet - 142,984 kilometers diameter - 11.21 Earths across
Calendar: 1 Jupiter year = 11.857 Earth years; 1 Jupiter day = 0.414 Earth days
Orbit: 778,570,000 kilometers - 5.204 Earth orbits
Axial tilt: 3.13 degrees (nearly vertical)