This is Prometheus

Prometheus is a small moon of Saturn that was discovered from images taken by the Voyager 1 spacecraft in 1980 and first photographed closely by the Cassini spacecraft in 2015.

As we can see from the image, Prometheus is an extremely elongated moon, measuring 140 x 80 x 60 km. Its surface is very irregular, with some mountains and valleys and several craters with a diameter of more than 20 km.

From the data obtained by the Cassini probe, a very low density and a very high albedo were deduced, which would seem to indicate that Prometheus is a body consisting mainly of icy water with several empty cavities inside it.

Prometheus is also a shepherd moon of the F Ring. Orbiting inside the ring the moon through its gravitational influence helps to keep the shape of the ring intact, which otherwise would disintegrate.

Despite this, the orbit of Prometheus turns out to be slightly chaotic due to orbital resonances with other moons of Saturn, in particular Pandora. In fact, every 6.2 years orbital resonances bring these two moons to be just 1400 km apart: as a result the orbit of Prometheus is slightly disturbed each time.

Credit: NASA, JPL, SSI.

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