![]() "Some dismissed Callisto as the most boring object of its size in the solar system," they added. In fact, Callisto was very heavily cratered compared with the other moons, the authors wrote. Callisto's density and temperature were refined, and images of the surface showed features as small as 1 kilometer per pixel - in other words, a resolution small enough to spot impact craters. It was the Voyager missions of the late 1970s that really showed us a different picture of the moon. Pioneer 10 and Pioneer 11 each flew by Jupiter and its moons in the early 1970s, but these missions didn't give much new information on Callisto beyond what Earth-based telescopes showed. (Image credit: Lunar and Planetary Institute/Arizona State University) The two landslides are about 3 to 3.5 km in length. Galileo images of the surface of Jupiter's moon Callisto have revealed large landslide deposits within two large impact craters. ![]() This led them to conclude that Callisto had a rocky surface. Callisto also had low reflectivity (albedo) and was known to have a low density, but astronomers saw no evidence of water emissions. From what astronomers could tell, the surface looked relatively featureless compared with Io and Ganymede. While telescopes improved substantially by the Space Age of the 1960s, still little was known about Callisto, according to the 2004 book " Jupiter: The Planet, Satellites and Magnetosphere (opens in new tab)" (Cambridge, 2007). Temperature: The mean surface temperature of Callisto is minus 218.47 degrees Fahrenheit (minus 139.2 Celsius). (Earth's moon is fifth largest, following Io.) It is the third largest moon in the solar system, after Ganymede and Titan. ![]() Size: At 3,000 miles (4,800 km) in diameter, Callisto is roughly the same size as Mercury. Callisto is tidally locked, so the same side always faces Jupiter. It also experiences fewer tidal influences than the other Galilean moons because it orbits beyond Jupiter's main radiation belt. It takes the moon about seven Earth-days to make one complete orbit of the planet. Callisto orbits Jupiter at a distance of about 1,168,000 miles (1,880,000 kilometers). The surface has not changed much since initial impacts molded its surface 4 billion years ago.ĭistance from Jupiter: It is the outermost of the Galilean moons. There is hardly any geologic activity on its surface. It is the most heavily cratered object in the solar system, according to NASA. Basic factsĪge: Callisto is about 4.5 billion years old, about the same age as Jupiter. The Medici moons were renamed Io, Europa, Ganymede and Callisto to avoid confusion by the mid-1800s. ![]() Over time, moons around other planets were discovered - and additional moons found around Jupiter. Also, all planets revolved around the sun. The moons and the planets were not unchanging and perfect for example, mountains seen on the moon showed that geological processes happened elsewhere. Galileo's observations of Jupiter's moons - as well as noticing that Venus went through "phases" similar to our own moon - gave compelling evidence that not everything revolved around the Earth.Īs telescopic observations improved, however, a new view of the universe emerged. At the time, the Catholic Church supported the idea that everything orbited the Earth, an idea put forth in ancient times by Aristotle and Ptolemy. The discovery had not only astronomical, but also religious implications. Individually they were called Jupiter I, II, III and IV, with "IV" referring to what we now call Callisto. For two centuries Jupiter's moons were (as a group) named after the Medicis, a powerful Italian political family, according to NASA. ![]() At the time, it was believed that the Earth was the only planet with a moon. The planet was not alone it had four moons circling it. 7, 1610, what he saw surprised everybody. When Galileo turned his telescope to Jupiter on Jan. ![]()
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