Jupiter is the fifth and largest planet in our solar system. Its about 5.2 times farther away from the Sun than Earth and - with 318 times the mass of Earth - twice as massive as all the other planets combined. It consists of 90% hydrogen and 10% helium and therefore can be described as a "gas giant" - giant planets without solid surfaces. Its very rapid rotation leads to massive wind systems, which divides the atmosphere into distinct zones and belts. Giant storm systems are embedded in these zones and belts, some of them stable for centuries like the "Giant Red Spot".
Until know we know of 16 moons of Jupiter, among them the well known four large Galilean Moons - the volcanoes of Io and the (assumed) salt-oceans of Europa and Ganymede are some of the most intriguing findings of the recent Jupiter exploration. Less well known are the rings of Jupiter, which are much smaller and dimmer than those of Saturn. Its magnetic field and magnetospehere are of gigantic proportions. Within the magnetosphere numerous processes are taking place:
- Radio waves are emitted due to the wave-particle interaction, which can be detected on Earth (e.g. in Graz).
- Io's volcanism deposits approximately 1000 kg/s of gas into Jupiter's magnetospere, which, after ionization, creates a torus around the planet, emitting mainly ultraviolet radiation.
- The Galilean moons interact with Jupiter's strong magnetic field, generating strong currents which create footpoints (bright spots) in the auroral regions.
In the summer of 1994, the broken-up comet Shoemaker-Levy-9 impacted Jupiter, leaving impact marks in the cloud cover for approximately 6 days. In summer 2009, Jupiter was again impacted near the south pole, leaving again a mark in the cloud cover.
The Galileo spacecraft arrived at Jupiter in December 1995 and after a very successful mission was plunged into Jupiter in September 2003. At arrival an entry probe was released, which for the first time provided in-situ data from Jupiter's atmosphere.
The NASA mission Juno was launched in 2011 and will enter into a Jovian orbit in 2016. ESA's first mission to the outer solar system JUICE is planned for launch in 2022 and will arrive at Jupiter in 2030.
Further information on Jupiter is found at The Nine Planets.