"On arrival to Jupiter, December 7th, 1995, Galileo became the first spacecraft to orbit around a gas giant planet, and the first to drop a probe into a giant planet's dense atmosphere. In the above Hubble Space Telescope image, the probe entry location is indicated by the arrow. The atmospheric probe relayed information about temperature, pressure, and composition for about an hour as it descended through Jupiter's clouds, while the orbiter spent at least two years exploring the Jovian system. Along with advancing our knowledge of Jupiter and its environs, Galileo data was expected to reveal some of the secrets of the formation and evolution of the Solar System."