Here's Why Saturn's Inner Moons Are Shaped Like Ravioli and Potatoes

The new finding may help to explain how moons in general may form, researchers said in a new paper describing the work.

The Cassini spacecraft, which studied the ringed planet up close for 13 years, revealed that unlike Earth's spherical moon, the small moons closest to Saturn had strange, irregular shapes. These odd forms range from Pan's and Atlas' ravioli-like shape to Prometheus' resemblance to a combination of Moby Dick, a potato and H. R. Giger's Alien skull. [Cassini Spacecraft Photographs Saturn's Strangest Moons]

Previous research had suggested ways in which each of these bizarre moons might have formed. 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 Space.com.Leleu's team ran computer simulations to see how the shapes of Saturn's inner moons might have evolved over time. The powerful effects of Saturn's gravitational pull were a key influence on these simulations.

The strange small moons of Saturn, as imaged by the Cassini spacecraft (top), compared to moons created through simulated collisions. 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.

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. "If that is the case and these bodies formed that way, it has important implications for formations of moons in general, because [previous research has shown] that the pyramidal scenario could be at the origin of most of the moons in the solar system," Leleu said.

The computer simulations also revealed the special environment in which Saturn's inner moons exist that makes near-head-on collisions frequent. "We found that 20 to 50 percent of the small moons should display either an equatorial ridge or an elongated shape, while the rest should have more random potato-like shapes," Leleu said. "And this is the case. Considering the six inner moons Pan, Atlas, Prometheus, Pandora, Janus and Epimetheus, the first three display these features, while the others — Pandora, Janus and Epimetheus — have random shapes."

TOPICS

Charles Q. Choi is a contributing writer for Live Science and Space.com. He covers all things human origins and astronomy as well as physics, animals and general science topics. Charles has a Master of Arts degree from the University of Missouri-Columbia, School of Journalism and a Bachelor of Arts degree from the University of South Florida. Charles has visited every continent on Earth, drinking rancid yak butter tea in Lhasa, snorkeling with sea lions in the Galapagos and even climbing an iceberg in Antarctica.