Wednesday, March 10, 2010

Closeup of Helene

Cassini acquired this interesting image of the satellite Helene on March 3. Helene is a small 30km-wide satellite of Saturn. Its orbit is also very curious, since it resides at the L4 Lagrange point of the much larger 1000km-wide satellite Dione. The L4 Lagrange point leads Dione's motion by 60 degrees in longitude. Such satellites are known as coorbitals, since they co-orbit with another larger body, and only a few such coorbital satellites are known. This coorbital motion is analgous to the Trojan asteroids, which lead/trail Jupiter by 60 degrees. Note also Helene's smooth surface. Although the outlines of large craters are clearly evident, their filled-in appearance suggests that this satellite is also being bombarded and coated by dust that might also be present in this part of the Saturnian system. Keep an eye on the CICLOPS website for information about this small but interesting satellite.

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