"But the small moons of Saturn are in a very specific environment - they are very close to Saturn and its rings, and on almost perfectly circular orbits, and almost all in the same plane." "For bodies such as comets or asteroids, the impact configuration that would form these equatorial ridges have a very low probability of happening," Leleu said. Study co-author Martin Jutzi, also of the University of Bern, had previously found that collisions between comets could lead to bodies with the flattened shapes and equatorial ridges seen on Pan and Atlas.
Mergers involving slightly more oblique impact angles resulted in elongated shapes resembling Prometheus. The computer simulations revealed that near-head-on collisions led to ravioli-like flattened objects with equatorial ridges, similar to the shapes of Pan and Atlas. "If that is the case and these bodies formed that way, it has important implications for formations of moons in general, because that the pyramidal scenario could be at the origin of most of the moons in the solar system," Leleu said.
#Moon atlas saturn series#
Instead, the researchers found that Saturn's inner moons likely formed through a series of collisions between tiny moonlets, known as the pyramidal regime formation scenario. (Image credit: NASA/JPL-Caltech/Space Science Institute/University of Bern) Not only are they similar shapes, but the model suggests why Pan's and Atlas' ridges look different: The ridges are made from smooth material squeezed out from the middle during the merger. The strange small moons of Saturn, as imaged by the Cassini spacecraft (top), compared to moons created through simulated collisions. The planet's powerful gravitational pull made it unlikely that Saturn's inner moons formed by gradual accretion of material around a core, "which is the go-to scenario for the formation of celestial bodies," Leleu told. As such, Saturn's inner moons experience huge tidal forces that can pull them apart, the researchers said. Saturn's mass is 95 times Earth's mass, and Saturn's inner moons orbit the giant planet at a distance of less than half that between Earth and its moon. The powerful effects of Saturn's gravitational pull were a key influence on these simulations. However, until now, researchers did not have an explanation that encompassed the whole range of these unusual shapes, study lead author Adrien Leleu, a dynamicist at the University of Bern in Switzerland, told 's team ran computer simulations to see how the shapes of Saturn's inner moons might have evolved over time. Previous research had suggested ways in which each of these bizarre moons might have formed. Saturn's moon Atlas got its flat, ravioli-like shape from the merging collision of two similar-size bodies, according to new research.
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