Cassini spots a small moon surfing through Saturn’s rings

Saturn has an extensive ring system that extends out to 282,000km away from the planet, or about three quarters of the distance between the Earth and the Moon. Within this structure there are a dozen or so significant gaps, one of which is the Keeler Gap located near the outer edge of the planet's main rings. The tiny moon Daphnis has cleared this gap, which measures just 42km across.

One of the main benefits of having an orbiting spacecraft in a planetary system is multiple opportunities to image fine features—such as the 8km-wide moon Daphnis grazing through this narrow gap. And on Monday, NASA's Cassini spacecraft captured an amazing view of this interaction as Daphnis grazed Saturn's rings.

The image shows a fairly smooth surface on the moon with a few craters. Intriguingly, the normally sharp edges of Keeler Gap show a wavy feature, which was likely caused by a close approach by Daphnis. Note the faint, narrow tendril of ring material trailing just to the left of Daphnis, which is likely due to Daphnis attracting this material out of its typical orbit.

This is not the first time Cassini has observed Daphnis perturbing Saturn's rings. Photos taken from different angles have shown the vertical component of waves created by Daphnis, suggesting they rise between 0.5 to 1.5km high, which towers far above the rings that are only about 10 or 20 meters thick.

Listing image by NASA/JPL-Caltech/Space Science Institute