Secrets of Saturn’s Mini ‘Ravioli’ Moons ⋆
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Secrets of Saturn’s Mini ‘Ravioli’ Moons

Data gathered by NASA’s Cassini spacecraft when it conducted a close flyby to Saturn during the final days of its mission have revealed new details on the planet’s nearby mini ‘ravioli’ moons.

The five tiny moons, which are located near Saturn’s rings, have strange surfaces that are covered with material from Saturn’s iconic rings and from ice particles blasting out of Saturn’s larger moon Enceladus, according to NASA. They also have an unusual shape — rather than being spherical, they are blobby and ravioli-like, with material stuck around their equators.

Mini Ravioli Moons!

This graphic shows the ring moons inspected by NASA’s Cassini spacecraft in super-close flybys: (Photo Credit: NASA-JPL/Caltech)

“We found these moons are scooping up particles of ice and dust from the rings to form the little skirts around their equators,” said Bonnie Buratti of NASA’s Jet Propulsion Laboratory. “A denser body would be more ball-shaped because gravity would pull the material in.”

The new research, detailed in a paper published in the journal Science, was based on data gathered by six of Cassini’s instruments before its mission ended in 2017.

We have known about Saturn since ancient times, of course, but we’ve only really known about the inner moons — known as Pan, Daphnis, Atlas, Pandora, and Epimetheus — pretty recently. Pan, for example, was discovered in 1985, while Daphnis only dates back to 2005.

Of the satellites studied, the surfaces of those closest to Saturn — Daphnis and Pan — were found to be the most altered by ring materials. Montage of views from NASA’s Cassini spacecraft shows three of the small, ring moons inspected during close flybys: Atlas, Daphnis and Pan. (Photo Credit: NASA / JPL-Caltech / Space Science Institute)

The key puzzle piece was a data set from Cassini’s Visible and Infrared Mapping Spectrometer (VIMS), which collected light visible to the human eye and also infrared light of longer wavelengths. It was the first time Cassini was close enough to create a spectral map of the surface of the innermost moon Pan. By analyzing the spectra, VIMS was able to learn about the composition of materials on all five moons.

VIMS saw that the ring moons closest to Saturn appear the reddest, similar to the color of the main rings. Scientists don’t yet know the exact composition of the material that appears red, but they believe it’s likely a mix of organics and iron.

The moons just outside the main rings, on the other hand, appear more blue, similar to the light from Enceladus’ icy plumes.

The flybys of the ring moons, performed between December 2016 and April 2017, engaged all of Cassini’s optical remote sensing instruments that study the electromagnetic spectrum. They worked alongside the instruments that examined the dust, plasma and magnetic fields and how those elements interact with the moons.

Scientists are still not sure what triggered the moons to form, but they will use the new data to model scenarios and could also apply the insights to small moons around other planets and possibly even to asteroids.  “Do any of the moons of the ice giant planets Uranus and Neptune interact with their thinner rings to form features similar to those on Saturn’s ring moons?” Buratti asked. “These are questions to be answered by future missions.”

Cassini’s mission ended in September 2017, when it was low on fuel. The spacecraft was deliberately plunged by mission controllers into Saturn’s atmosphere to avoid the risk of it crashing into the planet’s moons. NASA is expected to reveal more science from the Cassini’s last orbits, known as the” Grand Finale,” in the next few months.Sat