Impacts may have created Saturn's odd inner moons

A new study gives insight into how Saturn's strange inner moons first formed.
By Joseph Scalise | May 23, 2018
A team of astronomers from the University of Bern believe they have discovered why Saturn's small inner moons have such a peculiar shape, a new study published in Nature Astronomyreports.

Though most moons are typically round, Saturn's inner satellites appear much more like giant ravioli. While scientists have been aware of the odd shape since the Cassini spacecraft first recorded the bodies, nobody has found evidence on how they formed until now.

In the study, scientists discovered the odd shapes likely came about from merging collisions among similar-sized little moons. They made that discovery by running a series ofcomputer simulations based on older theories.

While the first few tests went by without a hitch, issues arose quickly after that.


"[W]e took the tidal forces into consideration and the problems piled up," said study lead author Adrien Leleu, a dynamicist at the University of Bern in Switzerland, according to

AsSaturn has 95 times more mass than Earth and the inner moons orbit the planet at less than half the distance between Earth and Moon, the tides they generate are incredibly powerful.

So much so that it isextremely unlikely Saturn's inner moons formed through gradual accretion of material around a single core. Rather, the models suggest that a series of moonlet mergers formed them.

That theory is backed up by simulations that showed moonletcollisions create shapes that perfectly match the images captured by Cassini.

Close to head-on mergers often create flattened objects with large equatorial ridges. In that way, such impacts could then have created the ravioli-like moons that exist today.

"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," added Leleu, according to "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."

This research sheds new light on the distant planet and gives astronomers more information about our solar system. Not only do scientists now have an idea of how the inner moons formed, but they also know Saturn has a special environment that results in more collisions.


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