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A new analysis of data from Cassini has confirmed that the tiny moons orbiting close to Saturn’s rings are repeatedly coated by material from those rings.
The new research, from data gathered by six of Cassini’s instruments before its mission ended in 2017, is a clear confirmation that dust and ice from the rings accretes onto the moons embedded within and near the rings.
Scientists also found the moon surfaces to be highly porous, further confirming that they were formed in multiple stages as ring material settled onto denser cores that might be remnants of a larger object that broke apart. The porosity also helps explain their shape: Rather than being spherical, they are blobby and ravioli-like, with material stuck around their equators. “We found these moons are scooping up particles of ice and dust from the rings to form the little skirts around their equators,” Buratti said. “A denser body would be more ball-shaped because gravity would pull the material in.”
This result is not a surprise. It has been hypothesized since the first images of these weirdly shaped moons (as illustrated by the picture of Pan from March 2017 above) were first beamed back by Cassini. This new analysis just helps confirm it.
I will add that searching through Behind the Black for that image of Pan made me realize how much I miss Cassini. I used to post lots of its images, always spectacular and breath-taking. With it gone, the images from Saturn have stopped, and will not resume for decades to come.