Calypso

One of three moons that share an orbit of Saturn nearly 300,000 km from the planet within the tenuous and icy ring known as the E Ring. The largest of these three is Tethys, a spherical moon more than a thousand kilometres in diameter, but Tethys also has two smaller companions. Calypso is one these, a fraction of Tethys' size and following that major moon in its orbit around Saturn by some sixty degrees of arc. It is able to hold a stable relative position because it occupies Tethys' trailing Lagrange Point. Calypso has a counterpart, Telesto, which precedes Tethys in its orbit by the same sixty degree angle that Calypso trails behind.

Physically Calypso is an irregular body, highly elongated in shape; it measures a little more than thirty kilometres along its longest axis, and less than fifteen kilometres along its shortest. Though rocky and cratered, its surface is also relatively smooth, with a tracery of flowing patterns. These effects are probably due to particles collected from the enveloping E Ring, particles whose ultimate origins lie in the great geysers blasting water ice outward from the moon Enceladus.