The Galilean moons are the four largest moons of Jupiter—Io, Europa, Ganymede, and Callisto. They were first seen by Galileo Galilei in December 1609 or January 1610, and recognized by him as satellites of Jupiter in March 1610. They were the first objects found to orbit a planet other than the Earth.
Callisto, or Jupiter IV, is the second-largest moon of Jupiter, after Ganymede. It is the third-largest moon in the Solar System after Ganymede and Saturn's largest moon Titan, and the largest object in the Solar System that may not be properly differentiated. Callisto was discovered in 1610 by Galileo Galilei. At 4821 km in diameter, Callisto has about 99% the diameter of the planet Mercury but only about a third of its mass. It is the fourth Galilean moon of Jupiter by distance, with an orbital radius of about 1883000 km. It is not in an orbital resonance like the three other Galilean satellites—Io, Europa, and Ganymede—and is thus not appreciably tidally heated. Callisto's rotation is tidally locked to its orbit around Jupiter, so that the same hemisphere always faces inward. Because of this, there is a sub-Jovian point on Callisto's surface, from which Jupiter would appear to hang directly overhead. It is less affected by Jupiter's magnetosphere than the other inner satellites because of its more remote orbit, located just outside Jupiter's main radiation belt.
Ganymede, a satellite of Jupiter, is the largest and most massive of the Solar System's moons. The ninth-largest object of the Solar System, it is the largest without a substantial atmosphere. It has a diameter of 5,268 km (3,273 mi), making it 26 percent larger than the planet Mercury by volume, although it is only 45 percent as massive. Possessing a metallic core, it has the lowest moment of inertia factor of any solid body in the Solar System and is the only moon known to have a magnetic field. Outward from Jupiter, it is the seventh satellite and the third of the Galilean moons, the first group of objects discovered orbiting another planet. Ganymede orbits Jupiter in roughly seven days and is in a 1:2:4 orbital resonance with the moons Europa and Io, respectively.
Pwyll is an impact crater on the surface of Jupiter's moon Europa. It is thought to be one of the youngest features on the moon. The crater was first observed from Voyager images in 1986, and the name was officially recognized by the IAU in 1997, after Pwyll of Welsh mythology.
Tempel 1 is a periodic Jupiter-family comet discovered by Wilhelm Tempel in 1867. It completes an orbit of the Sun every 5.5 years. Tempel 1 was the target of the Deep Impact space mission, which photographed a deliberate high-speed impact upon the comet in 2005. It was re-visited by the Stardust spacecraft on February 14, 2011 and came back to perihelion in August 2016.
Linae is Latin for 'line'. In planetary geology it is used to refer to any long markings, dark or bright, on a planet or moon's surface. The planet Venus and Jupiter's moon Europa have numerous lineae; Pluto and Saturn's moon Rhea have several.
Kittu crater is a crater on Jupiter's moon Ganymede. It is approximately 15 km (9.3 mi) in diameter.
Neith crater is a crater on Jupiter's moon Ganymede, the largest moon in the solar system.
Nergal crater is a crater on Jupiter's moon Ganymede. It has a distinctive ejecta blanket surrounding it that's darker nearer the craters and brighter further away. The inner region of the ejecta is characterized by a lobate appearance indicative of the flow of a liquid substance over the surface. The flow was probably icy surface material melted by the energy released during the impact that formed the crater.
Located on Jupiter's moon Callisto, Valhalla is the largest multi-ring impact crater in the Solar System. It is named after Valhalla, the hall where warriors are taken after death in Norse mythology.
A crater chain is a line of craters along the surface of an astronomical body. The descriptor term for crater chains is catena, plural catenae, as specified by the International Astronomical Union's rules on planetary nomenclature.
Enki Catena is a crater chain on Ganymede measuring 161.3 kilometres (100.2 mi) long.
Galileo Regio is a large, dark surface feature on Jupiter's moon Ganymede.
Memphis Facula is a palimpsest, or "ghost crater", on Ganymede, the largest of the Jovian satellites.
Lofn is a large relatively young impact crater on Jupiter's Galilean satellite Callisto. It was identified in 1997 and named after the goddess of marriage in Norse mythology. Located near the south pole of this moon, Lofn is classified as a flat floored or anomalous dome impact crater. It is superimposed on Adlinda multilayer structure obscuring about 30% of it. Another multi-ring structure—Heimdall is found to the south-west of Lofn.
The following outline is provided as an overview of and topical guide to Jupiter:
Epigeus is the largest known impact crater on Jupiter's Galilean satellite Ganymede, with a diameter of 343 km. It is 6.5% the mean equatorial diameter of Ganymede, 5,270 km (3,270 mi). It is located in Marius Regio at 22.96°N 179.35°E.
This article is intended to provide an overview of various aspects of the tectonics on icy moons.
In modern times, numerous impact events on Jupiter have been observed, the most significant of which was the collision of Comet Shoemaker–Levy 9 in 1994. Jupiter is the most massive planet in the Solar System and thus has a vast sphere of gravitational influence, the region of space where an asteroid capture can take place under favorable conditions.
