First of all, get your mind out of the gutter. 😉 21-mile (35 km) -wide Helene is a “Trojan” moon of the much larger Dione, so called because it orbits Saturn within the path of Dione, 60º ahead of it. (Its little sister Trojan, 3-mile-wide Polydeuces, trails Dione at the rear 60º mark.) The Homeric term comes from the behavioral resemblance to the Trojan asteroids which orbit the Sun within Jupiter’s path…again, 60º in front and behind. These orbital positions are known as Lagrangian points (L4 and L5, respectively.)
The image here shows some really interesting texture on Helene…grooves running outwards from a central point on the little moon. I’m not sure what side of Helene we are looking at here, but it would make sense if this were its leading face that we are seeing the result of motion into its orbit, perhaps the result of meteorite weathering or some other debris falling onto it along its path, maybe material ejected from Dione?
This is a crop of a raw image acquired by the Cassini spacecraft on January 31, 2011, during a flyby of several moons in the Saturnian system. Cassini also visited Mimas and Enceladus, getting some very nice images of those worlds as well…I’ll post some of those later today!
This isn’t the closest Cassini has come to Helene, either…that happened back in March of 2010 when it passed by at a distance of about 1,200 miles (1,900 km).
Image: NASA / JPL / Space Science Institute. Edited by J. Major.
Update: the image above is now an RGB color version, assembled from three separate raw images.