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. Over time, moons around other planets were discovered — and additional moons found around Jupiter. [6] Its surface composition is thought to be broadly similar to its composition as a whole. The Galileo orbiter completed the global imaging of the surface and delivered a number of pictures with a resolution as high as 15 meters of selected areas of Callisto. [35][36][37] [24][81], The study proposed a possible surface base on Callisto that would produce rocket propellant for further exploration of the Solar System. [25] The name was suggested by Simon Marius soon after Callisto's discovery. The density and moment of inertia for an equilibrium Callisto are compatible with the existence of a small silicate core in the center of Callisto. [18] Instead of small craters, the almost ubiquitous surface features are small knobs and pits. An upcoming mission called JUICE (Jupiter Icy Moon Explorer) will focus on three icy Jupiter moons, including Callisto, to get more information about its environment. The moons and the planets were not unchanging and perfect; for example, mountains seen on the moon showed that geological processes happened elsewhere. [21] The allowable timescale of formation of Callisto lies then in the range 0.1 million–10 million years. Callisto was a nymph (or, according to some sources, the daughter of Lycaon) who was associated with the goddess of the hunt, Artemis. [15] Explanations that have been proposed for the contrasts in internal heating and consequent differentiation and geologic activity between Callisto and Ganymede include differences in formation conditions,[68] the greater tidal heating experienced by Ganymede,[69] and the more numerous and energetic impacts that would have been suffered by Ganymede during the Late Heavy Bombardment. [50] Many fresh impact craters like Lofn also show enrichment in carbon dioxide. Please deactivate your ad blocker in order to see our subscription offer. "Some dismissed Callisto as the most boring object of its size in the solar system," they added. Orbit and Rotation [45][46], The average density of Callisto, 1.83 g/cm3,[4] suggests a composition of approximately equal parts of rocky material and water ice, with some additional volatile ices such as ammonia. [80] Advantages of a base on Callisto include low radiation (due to its distance from Jupiter) and geological stability. [22] In this case the water+ice layer can be as thick as 250–300 km. For two centuries Jupiter's moons were (as a group) named after the Medicis, a powerful Italian political family, according to NASA. Callisto is a large moon orbiting Jupiter. It is the fourth Galilean moon of Jupiter by distance, with an orbital radius of about 1883000 km. Its orbit is very slightly eccentric and inclined to the Jovian equator, with the eccentricity and inclination changing quasi-periodically due to solar and planetary gravitational perturbations on a timescale of centuries. [14][22] A salty ocean 150–200 km deep may lie beneath the crust,[14][22] indicated by studies of the magnetic fields around Jupiter and its moons. Due to the convection process, however, very slow and partial separation and differentiation of rocks and ices inside Callisto has been proceeding on timescales of billions of years and may be continuing to this day. Compounds detected spectroscopically on the surface include water ice,[13] carbon dioxide, silicates, and organic compounds. Please refresh the page and try again. This asymmetry may originate from a different hydrogen abundance in both leading and trailing hemispheres. [11] The radiation level at Callisto's surface is equivalent to a dose of about 0.01 rem (0.1 mSv) per day, which is over ten times higher than Earth's average background radiation. Callisto orbits Jupiter at a distance of about 1,168,000 miles (1,880,000 kilometers). The moon has been a subject of several flybys, including the long-running Galileo mission at Jupiter in the 1990s and 2000s. New York, [14][22] The exact composition of Callisto's rock component is not known, but is probably close to the composition of L/LL type ordinary chondrites,[14] which are characterized by less total iron, less metallic iron and more iron oxide than H chondrites. Thank you for signing up to Space. 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. Like Europa and Ganymede, as well as Saturn's moons Enceladus, Dione and Titan and Neptune's moon Triton, a possible subsurface ocean might be composed of salt water. As mentioned above, small patches of pure water ice with an albedo as high as 80% are found on the surface of Callisto, surrounded by much darker material. Beneath the lithosphere and putative ocean, Callisto's interior appears to be neither entirely uniform nor particularly variable. [18] At a small scale, the surface is varied and made up of small, sparkly frost deposits at the tips of high spots, surrounded by a low-lying, smooth blanket of dark material. While Juno is more designed to look at the atmosphere and environment of Jupiter, it has taken some images of Callisto from a distance. 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