Moons in the Night

Two of Saturn's moon appear to meet in the night sky with the faint band called the E ring sunlit behind them. But although they appear close - and to my eyes Tethys seems closer to the camera - it's not so:

Enceladus (505 kilometers, or 314 miles across) and Tethys (1,071 kilometers, or 665 miles across) appear close together in the sky in this image, but in reality, Tethys was more than 260,000 kilometers (162,000 miles) farther from the Cassini spacecraft -- greater than the distance from Earth to the Moon. Enceladus is easy to identify by the brilliant plume of ice erupting from its south pole.

Although this perspective views the night sides of both moons, the Sun is not the only source of illumination in the Saturn system. Tethys is at a fuller phase with respect to Saturn, and thus its "night side" is more fully lit than that of Enceladus.

(Compare this shot with Rhea and Enceladus I posted last summer.)