![]() ![]() Scientists are hoping to learn more about this feature to better explain similar events on Earth and Mars.īoth hemispheres contain a number of impact craters of varying sizes. Given that Iapetus does have a high peak and the longest landslides were associated with the ridge (and related features), it's likely this would have been the cause. These were likely generated when material fell from a great height and travelled a long way in the light gravity of the moon. In 2012, scientists announced they had detected landslides of up to 50 miles. There are, however, other signs of change on its surface. As a result, the skin of the satellite does not show signs of melting and resurfacing that may have smoothed the outer layer of other moons. Unlike other, closer moons, Iapetus suffers very little tidal heating from the massive planet. Iapetus travels around Saturn at a distance of 2,213,000 miles (13,561,300 km) from Saturn, the most distant of its major satellites. It may also have been created from material deposited by a ring or moon that collapsed onto the satellite. The ridge wrapped around Iapetus' equator may have formed early in its history, when the moon spun faster than it does today. The Voyager Mountains reach as high as 6 miles (10 kilometers). The other mountains are covered with dark material. The white dots spotted by Voyager were not peaks but regions of ice on their eastern sides. Years later, NASA's Cassini probe studied the ridge in depth. Some of the peaks reach heights exceeding 12 miles (20 km), making them among the highest mountains in the solar system.Ī line of white dots making up the ridge, informally called the Voyager Mountains, was first spotted and studied in the early 1980s by the spacecraft of the same name. The ridge stretches more than 800 miles (1,300 km) around the moon's 2,871-mile (4,621 km) equatorial circumference. (Image credit: NASA/JPL/Space Science Institute)Ī chain of high mountains circle the equator, stretching more than halfway around the moon, though in it may have encircled it completely long ago. This image reveals mountains only about half that height. The equatorial ridge of Iapetus can reach heights of up to 12 miles (20 km). Although its radius is about two-fifths that of Earth's moon, its icy composition means that it is only about 2 percent as massive. Iapetus is the third-largest moon orbiting Saturn, with a diameter of 914 miles (1,471.2 km). ![]() Over time, the satellite's spin would have slowed until it eventually became tidally locked. Early in its life, when the moon still spun rapidly, a thick crust could have frozen the moon into its odd shape. However, its odd shape could easily have a natural explanation. The angular structure of the moon has led to conspiracy-like suggestions that it is not a natural satellite but could have been built or modified by another civilization. The squashed shape of the moon resembles a satellite that rotates once every 10 hours, rather than the 79 days it takes Iapetus to make a full revolution. The walnut-shaped moon is not spherical, but has a bulging equator with squashed poles. Iapetus has a low density of only 1.083 grams per cubic centimeter, just a little more than liquid water, implying that it composed primarily of water, with rock making up less than a quarter of its composition. ![]() Nearly 200 years later, John Herschel suggested that the moons around the ringed planet be named for the Titans, the siblings of the Greek god Cronus, who was Saturn to the Romans. Distant Iapetus started out as Saturn V, but the discovery of Mimas, Enceladus, and Hyperion bumped it down to Saturn VIII. For years, the moons were referred to numerically, based on their distance from Saturn. The pattern repeated itself over the course of the moon's 79-day orbit, leading Cassini to surmise that the moon was tidally locked, with one face darker than the other.Ĭassini named the four moons that he discovered (Iapetus, Rhea, Dione, and Tethys) the Sidera Lodoicea, or the Stars of Louis, after King Louis XIV. He first spotted it on the west side of the planet, but when he attempted to observe it 39 days later on the eastern side, no trace of the satellite could be found. But the icy moon challenged the Italian astronomer. Iapetus is one of four moons discovered by Giovanni Cassini in 1672. ![]()
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