Little Helene. Image: NASA/JPL/Space Science Institute

Here’s one of the small moons of Saturn we don’t get to see too much of, named Helene.   Helene is pretty small as moons go, only 20 miles across.   Cassini did a pass at just a bit more than 1,300 miles and that is about as close as the spacecraft has come to the little moon.  The moon is a little off center,  it’s not easy getting these shots sometimes.  The moon appears very bright because it is bathed in reflected light from Saturn.  There are other images, but they need to be processed by the Cassini team before they can be used, you can see them in the raw images section of the Cassini site (linked below), and you will understand what I am talking about.  I included an image from 2007 which you can see by clicking the image above AND there is going to be another flyby in April so hopefully the angles will be better. Still a good picture though.

Anyways, Helene is notable because it is what is known as a Trojan moon, meaning it is gravitationally tied to a larger moon, in this case, Dione, and Helene stays 60 degrees (400,000km/250,000 miles) ahead of the larger moon.

One of the big questions is:  how did this moon come to be gravitationally tied to Dione, maybe it blown off another in an impact.  Another is: is the moon’s leading edge coated with material from the “E” ring.

Have a look at the press release here.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.