Saturn’s inner moons are truly remarkable, as we have had the opportunity to witness through the eyes of NASA’s Cassini spacecraft. During its 13 years of imaging the gas giant, the space probe has sent back epic images of Saturn and its moons, revealing their confounding appearance.
The bizarre shapes of Saturn’s inner moons have been compared to anything from food, such as empanadas and pierogis, to cigars and even Moby Dick.
For instance, Pan and Atlas, which are both shaped like disks with bulging middles, have “unique ‘ravioli-like’ forms,” notes a new study published yesterday in the journal Nature Astronomy. At the same time, Pan has been described as a walnut, while Atlas has been likened to a flying saucer.
Meanwhile, Saturn’s moon Prometheus has inspired comparisons to a whale. The moon’s elongated shape is also evocative of a cigar and, according to Space.com, has been noted to resemble the alien skull created by H.R. Giger for Ridley Scott’s 1970 Sci-Fi movie.
“Closest to Saturn, these bodies provide important clues regarding the formation process of small moons in close orbits around their host planet, but their range of irregular shapes has not been explained yet,” the authors write in their study.
To shed light on the matter once and for all, a team of scientists from the University of Bern in Switzerland, performed computer simulations that traced the evolution on Saturn’s inner moons through time and finally found an answer to their odd and irregular shapes.
The computer models revealed that Saturn’s small inner moons were formed through a series of collisions between moonlets of similar sizes that eventually merged into the Pan, Atlas, and Prometheus we know today.
Based on the type and angle of the collision, these moons got either a flattened shape, which is what happened to Pan and Atlas, or an elongated form, as is the case with Prometheus, Phys.org reports.
Here’s the science behind all of this.
Saturn is the second-largest planet in our solar system, after Jupiter. The gas giant is 95 times more massive than Earth, which means that it exerts a far greater gravitational force than the one which shaped our moon.
“The conditions close to Saturn are very special,” says study co-author Martin Jutzi.
Because of Saturn’s powerful gravitational pull, coupled with the huge tidal forces that the planet unleashes upon anything that gets caught in its gravitational field, these moons couldn’t have formed through the gradual accretion or the build-up of material around a nucleus.
By using a computer model called the pyramidal regime formation scenario, the team discovered that Saturn’s three inner moons were born after similar-sized moonlets crashed into one another.
Head-on collisions gave rise to the ravioli-like shape of Pan and Atlas, distinguished by their equatorial ridges, whereas impacts at slightly more oblique angles eventual churned out the stretched out, 56-mile long Prometheus.
As study lead author Adrien Leleu explains, such impact configurations are uncommon among other celestial bodies, such as comets or asteroids. However, due to the “very specific environment” in which Saturn’s inner moons exist — their close proximity to their host planet and its rings, coupled with their “almost perfectly circular orbits” — near-head-on collisions would have been quite frequent in their case.
“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,” he pointed out.