National Aeronautics and Administration

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www..gov is the largest and most massive in our solar sys- Jupiter’s four largest , , , and Cal- SIGNIFICANT DATES tem, containing more than twice the amount of material of the listo — were first observed by the Galilei in 1610 — makes the first detailed observations of other bodies orbiting our combined. Most of the material 1610 using an early version of the . These four moons Jupiter. left over after the formation of the Sun went to Jupiter, forming a are known today as the Galilean . Galileo would be 1973 — becomes the first to cross the type of planet called a giant. astonished at what we have learned about these moons, largely belt and fly past Jupiter. from the NASA mission named for him: Io is the most volcani- Jupiter’s appearance is a tapestry of colorful bands and 1979 — and 2 discover Jupiter’s faint rings, several cally active body in the ; Ganymede is the largest spots. Most visible are composed of and am- new moons, and volcanic activity on Io’s surface. in the solar system and the only moon known to have its monia compounds, with unknown chemicals providing color. 1994 — observe as pieces of Shoemaker– own ; and a liquid- with the ingredi- Jupiter’s fast — spinning once every 10 — creates Levy 9 collide with Jupiter’s southern hemisphere. ents for may lie beneath the frozen of Europa, making it strong jet streams, smearing its clouds into bands across the 1995–2003 — The Galileo spacecraft drops a probe into Jupi- a tempting place to explore. planet. ter’s and conducts extended observations of Jupiter Discovered in 1979 by NASA’s Voyager 1 spacecraft, Jupiter’s and its moons and rings. With no surface to slow them down, Jupiter’s spots can rings were a surprise, as they are composed of small, dark par- 2007 — Images taken by NASA’s spacecraft, persist for many . The Great Spot, a swirling oval of ticles and are difficult (but not impossible) to see except when on the way to , show new perspectives on Jupiter’s clouds twice as wide as , has been observed on the gi- backlit by the Sun. Data from the Galileo spacecraft indicate atmospheric , the rings, volcanic Io, and icy Europa. ant planet for more than 300 years. More recently, three smaller that Jupiter’s may be formed by dust kicked up as 2009 — On July 20, almost exactly 15 years after fragments of ovals merged to form the Little Red Spot, about half the size of interplanetary smash into the ’s small comet Shoemaker–Levy slammed into Jupiter, a comet or aster- its larger cousin. Scientists do not yet know if these ovals and innermost moons. oid crashes into the giant planet’s southern hemisphere, creating planet-circling bands are shallow or deeply rooted to the interior. a dark scar. In December 1995, NASA’s Galileo spacecraft dropped a probe The composition of Jupiter’s atmosphere is similar to that of the into one of the dry, hot spots of Jupiter’s atmosphere. The probe ABOUT THE IMAGES Sun — mostly and . Deep in the atmosphere, made the first measurements of the planet’s composition 1 A natural-color and increase, compressing the hydrogen 1 2 and . Galileo studied Jupiter and its largest moons until image taken by the gas into a liquid. This gives Jupiter the largest ocean in the solar 2003. Beginning in 2016, NASA’s spacecraft will conduct Cassini spacecraft as system — an ocean made of hydrogen instead of water. Scien- 3 an in-depth investigation of the planet’s atmosphere, deep struc- it flew by on its way to tists think that, at depths perhaps halfway to the planet’s center, . Europa’s shad- ture, and for clues to its origin and . 4 the pressure becomes so great that electrons are squeezed off ow can be seen against the hydrogen atoms, making the liquid electrically conducting. FAST FACTS the planet’s cloud tops. Jupiter’s fast rotation is thought to drive electrical currents in 2 A Voyager 1 image of Jupiter’s . this region, generating the planet’s powerful magnetic field. It is Namesake King of the Roman gods still unclear if, deeper down, Jupiter has a central core of solid Mean Distance from the Sun 778.41 million km 3 A Hubble image of Jupiter’s material. (483.68 million mi) complex, glowing . The bright spot with a curving tail at Period 11.8565 Earth years the right is the auroral footprint of the moon Io. The Jovian magnetosphere is the region of space influenced by (4,330.6 Earth days) 4 An artist’s rendering of Jupiter’s inner magnetosphere, Jupiter’s powerful magnetic field. It balloons 1 to 3 million kilo- Orbit Eccentricity ( = 0) 0.04839 showing magnetic field lines (connecting the and south meters (600,000 to 2 million miles) toward the Sun and tapers Orbit Inclination to 1.305 deg poles) and , along with a region of intense radiation into a windsock-shaped tail extending more than 1 billion kilo- Inclination of to Orbit 3.12 deg around the planet’s middle. meters (600 million miles) behind Jupiter, as far as Saturn’s orbit. 9.92 hr The magnetic field rotates with the planet and sweeps up par- Equatorial Radius 71,492 km (44,423 mi) FOR MORE INFORMATION ticles that have an electric charge. Near the planet, the magnetic 317.82 of Earth’s field traps a swarm of charged particles and accelerates them to 1.33 g/cm3 solarsystem.nasa.gov/jupiter very high energies, creating intense radiation that bombards the 20.87 m/sec2 (68.48 ft/sec2) solarsystem.nasa.gov/planets/profile.cfm?Object= innermost moons and can damage spacecraft. Atmosphere Components hydrogen, helium Jupiter&Display=Moons at 1 bar –108 deg C (–163 deg F) With four large moons and many smaller moons, Jupiter forms a Known Moons* 50 kind of miniature solar system. In total, the planet has more than Rings 1 (three major components) 60 moons, including several that were discovered in just the past few years. *Plus 17 awaiting official confirmation, total 67, as of July 2013.

LG-2013-07-573-HQ — JPL 400-1489L 07/13