Saturn's "ring moons" in the form of ravioli could be formed as a result of a giant impact

During the last days of the legendary Cassini mission, NASA's spacecraft conducted a series of orbits around Saturn, capturing unprecedented images of the enigmatic enigmatic moons of the gas giant. These photos and other data have now been analyzed by astronomers, shedding new light on these elusive objects and the origin of the majestic rings of Saturn.

Saturn has about 60 known moons, of which a small handle is parked inside the planet's cyclic system or interacts closely with it. The new research published today in Science suggests new insights into five of these moons, Pan, Daphnis, Atlas, Pandora and Epimetheus, including details of their form and composition. The new paper, led by Bonnie Buratti of NASA's Jet Propulsion Laboratory and the California Institute of Technology, also provides new information on Saturn's ring system and its possible evolution.

The six orbits surrounding the Cassini ring took place between December 2016 and April 2017. The mission will end in September 2017 when the spacecraft deliberately struck Saturn. The images taken by Cassini were superb, showing unique moons.

Take Pan, for example, an 8 km wide moon with distinctive grooves on its surface and a domed equatorial ridge reminiscent of a tutu. Daphnis sits in a precarious orbit in a hole in the ring of Saturn. It also features a "skirt" around its equator.

Indeed, these five inner moons, none of which are wider than twenty kilometers, are quite strange and have unconventional shapes, surface features and colors. Moreover, they seem to have a close but poorly understood relationship with the rings of Saturn. With new Cassini data and unprecedented close-up images, Buratti and his colleagues were able to take a closer look at these mysterious objects.

"We were trying to understand the relationship between the moons and the main system," Buratti told Gizmodo. "Mainly, are they identical?"

Buratti and his colleagues were also looking for clues as to whether the rings of Saturn were formed as a result of a celestial collision and whether the abundant amount of material in the rings had given birth to the moons. Indeed, the disk of rock and ice around Saturn could be analogous, and involve similar processes, to the protoplanetary disk of the Sun (from which the planets, including the Earth, were formed) during the first days of the solar system. . Finally, the researchers hoped to see if there were volatile chemicals other than ice water in these circular moons.

According to the analysis, the distinctive geology of these five moons resulted from a complex, multi-stage process in which objects were formed from a ring-free material freezing. Strong tidal pressures and slow accumulation of ring-shaped particles have resulted in furrows and ridges on the surface. It therefore seems that the moons and the ring system have formed from a giant impact.

"Moons are giant fragments left by the impact," Buratti told Gizmodo. "The 'skirts' around their equators are particles of rings that continue to grow. The way moons flush particles into their path could be a smaller example of how planets form from smaller particles. "

As for the strange colors, Pan is the most red while Epimetheus is the most blue. Buratti is said to be "quite surprised by the red color of Pan," noting that the moons "blush as you approach Saturn, suggesting that their surfaces have accumulated annular particles." The chemicals responsible for the colors, and the processes involved are not yet well understood, but it could act as red chromophores, a mixture of organic matter and iron. The ice particles or water vapor of the Saturn E ring and the volcanic plume water vapor on Saturn's Enceladus moon could be contributing factors, according to the newspaper.

"The study confirms the impact of ice particles from Enceladus plumes on the Saturn system," said Tracy Becker, Planetary Scientist at the Southwest Research Institute, who was not involved in the new study, said to Gizmodo. "It's fascinating to see how these tiny particles actually change the color and freshness of Enceladus's closest moons, and also intriguing how Saturn's rings protect embedded satellites from some of these particles."

With regard to volatile substances other than water ice, none was found on the surface of circular moons.

"The presence of molecules more volatile than water ice would indicate a material coming from a colder region outside the Saturnian system," the authors wrote in this new study. "For example, the discovery of CO2 ice on the irregular outer moon Phoebe suggested that it came from the Kuiper belt."

The absence of volatile substances is therefore further proof that ringed moons formed in the rings and were not picked up by the intense gravity of Saturn.

"The results of this article help us better understand the complex cosmic interaction at work in the Saturnian system," said Gizmodo Tanya Harrison, an astronomer at Arizona State University and unaffiliated with the new study. . "Moons, ring particles and even Saturn itself interact to create unique worlds and environments in our solar system."

Harrison explained that the most interesting part of the study is that the odd-shaped moons in the shape of ravioli – Pan, Daphnis and Atlas – have acquired their appearance by collecting mostly particles of ice and dust from the rings of Saturn around of their equators as they moved in their orbit. As far as his favorite moon ring is concerned, this distinction belongs to Pan.

"I want to know what it's like to stand at the base of your belt and look at it," she says, "it looks pretty stiff, so I imagine it's a bit like The Wall in Game of thrones. "

Like Becker, Becker intrigues Becker, especially the variations observed along his equatorial crest. She wants to know why the thickness and the extent of the ridge are so variable around its surface. Becker said that future studies should examine this issue and determine how and from where the ring particles are collected on the surface of the moon.

Another interesting (but not totally surprising) observation, Harrison said, is that the closer a moon is to Enceladus, the more blue it is, probably because of the ice and water vapor that escapes. Southern geysers of Enceladus.

"That kind of stuff makes up the Saturn E ring and the 'snow' goes down in the neighboring moons," Harrison told Gizmodo. "Enceladus is sowing disorder in the Saturnian system, even though it is beautiful."

The new document is also important, Becker said, in the way that the rings of Saturn can be used as a proxy for the discs surrounding the young stars where the planets are formed, including the beginning of our own solar system.

"Having images and measurements of the satellites embedded in the rings is one of the best ways imaginable of learning how planets form, grow and interact with the disc," Becker said.

Saturn is without a doubt one of the most fascinating and intriguing objects in the entire solar system. It contains worlds in worlds and, thanks to Cassini, we are lucky to be able to witness these foolish places.

[Science]