Saturn’s moons Enceladus and Dione are caught in an endless race which Dione can never win.

In this image taken by the Cassini orbiter currently studying Saturn and its rings and moon, the larger – and more distant – Dione (700 miles or 1,126 kilometers in diameter) serves as a background for the Saturnian moon Enceladus, which passes between it larger cousin and parent planet.

With a diameter of 314 miles (505 kilometers), Enceladus is slightly less than half the width of Dione and is closer to Saturn, allowing the satellite to consistently pass Dione during its orbit.

Appearing to hover below both Dione and Enceladus are Saturn’s narrow F ring along the outer edges of the ring structure seen here.

·         Special Report: Cassini’s Mission to Saturn and its Moons

-- SPACE.com Staff

Credit: NASA/JPL/Space Science Institute