Callisto is one of the Galilean moons that orbit Jupiter.The Italian astronomer and physicist Galileo Galilei first discovered this satellite and Jupiter’s other satellites, Io (the most volcanically active moon), Europa, and Ganymede, on January 8, 1610. Callisto orbits the outermost shell of Jupiter and is considered the third-largest satellite of our Solar System.The discovery of Callisto, along with other Galilean moons, made us reckon with the fact that all the planets revolve around the Sun in our Solar system and not the other way round. Numerous religious beliefs were also associated with its discovery.All the Galilean moons were called Medicean planets, named after an Italian Medici family by Galileo himself. He also used the numeric system to name the moons, which was prevalent at that time. Jupiter’s moon Callisto was named Jupiter IV by him. The name Callisto came from Greek mythology, where a nymph named Callisto was in love with Zeus. When his wife Hera found out about their affair, she turned Callisto into a bear, who Zeus later made a part of the constellation Ursa Major.If you are enjoying the read, then make sure to check out Titania moon and Nix (moon) facts here on Kidadl.Moon Callisto: Physical featuresSeveral Galileo images captured that Callisto is tidally locked within Jupiter’s main radiation belt. Therefore, the same face of Callisto is always pointing towards Jupiter. Callisto orbits Jupiter with an orbital speed of 18,400 mph (29,612 kph). According to NASA, Callisto’s surface hardly experiences any geological activity. Therefore, no significant change occurred on its surface after its initial formation about four and a half billion years ago. It is the same age as that of Jupiter.The Galileo spacecraft provided a lot of information about Jupiter and the Jovian system. It helped us to understand how Callisto appears. Among the four Galilean moons, Callisto is heavily cratered due to having no geological activity. There are huge impact craters, of which Valhalla is the largest. Apart from these large impact craters, there are small craters as well on some of the parts of Callisto. It is bigger than the dwarf planet Pluto. It is also important to mention that Callisto is not affected by the gravitational pull of the other moons of Jupiter, including Europa and Ganymede. Callisto experiences less tidal heating due to this.Moon Callisto: CompositionCallisto’s surface is made up of water, ice, hydrocarbon compounds, carbon dioxide ice, silicate dust, and rock particles. It has 40% ice and 60% solid rock or iron surface. Just like other icy moons of Jupiter, Callisto has a thick icy surface that is heavily cratered. Callisto’s interior comprises layers of rock mixed with ice.The cratered surface of Callisto is tidally locked in Jupiter’s atmosphere in the outer solar system. The Galileo spacecraft also provided some fascinating information about the largest moon of Jupiter, Ganymede, and its other moons. Callisto may have a subsurface ocean. This possibility of a salty ocean underneath led scientists to think of the probability of sustaining life on this hunk of ice and rock.Did you know that the mass of Callisto was never a part of Jupiter? The question that now pops up in mind is why Callisto, along with other satellites of Jupiter, orbit around this large gaseous planet when they are not a part of it! This is because Jupiter’s moons are formed from the accreting gas along with the solid debris of the atmosphere of Jupiter. Thus, its satellites have developed from the circumplanetary disc of gases that compressed due to pressure build-up. This disc of gases and solid debris is basically the remnants of Jupiter after it was formed.Moon Callisto: Temperature And Surface ConditionsThe Galileo spacecraft detected the presence of a thin atmosphere surrounding Callisto, just like the largest moons of all the eight planets. More research on this thin atmosphere reveals that traces of oxygen and hydrogen are present in the exosphere layer. This, along with the presence of the salty ocean underneath, can lead to future human exploration of Callisto in search of life’s existence in the Solar system other than the Earth.This layer of atmosphere around Callisto also contains carbon dioxide. The surface ice on this moon bears carbon dioxide as well. Temperature conditions here are thus extremely harsh, with approximately minus 218.47 ℉ (-139.2 ℃). Less heat is dissipated on its surface because of less interaction with Jupiter’s magnetosphere. Also, a meager amount of radiation from the Sun reaches Callisto, making it favorable for life support. However, more recent researches claim that Europa, another satellite of Jupiter, may have better conditions than Callisto.NASA’s Hubble Space Telescope reveals that Jupiter’s auroral bursts were affected by Callisto. Evidence of the presence of ocean water underneath its surface is also found when fluctuations of its magnetic field were observed that implied the presence of electrical currents conducted from the salty ocean.Moon Callisto: Known For And The Distance Of Moon Callisto From EarthCallisto’s distance from Jupiter is about 1169855.54 mi (1,882,700 km), while its distance from the Earth is approximately 390.4 million mi (628.3 million km). Its orbit distance from Jupiter is bigger than Ganymede’s orbit radius. Callisto takes about 16.7 Earth days to orbit Jupiter. Did you know that Callisto has even lower gravity than Moon? This means that something weighing six pounds on Callisto will weigh a lot more on our Moon!Callisto is known for its heavily cratered surface, encompassed by concentric rings of ice. The tenuous atmosphere composed of traces of oxygen, carbon dioxide, and hydrogen reveals the possibility of life sustenance in the Jovian system. It is also known for being the third-largest satellite in the entire Solar system, followed by Ganymede and Titan.Its surface appears exceptionally bright because of thick ice that reflects sunlight more than our Moon does. Therefore, it appears more illuminated than the Moon when viewed through a telescope. When we compare its diameter with the planet Mercury, Callisto is only 36.2 mi (58.4 km) less than it. However, Mercury’s mass is three times more than that of Callisto.Here at Kidadl, we have carefully created many interesting family-friendly facts for everyone to enjoy! 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Callisto is one of the Galilean moons that orbit Jupiter.
