Telesto and Calypso are orbiting exactly in Tethys' orbit, but Telesto is 60 degrees ahead of Tethys and Calypso is 60 degrees behind it, at the Lagrange points created by the gravitational interaction of Tethys and Saturn. A similar gravitational interaction between Jupiter and the Sun is the cause of the Trojan asteroids' similar orbits, and as a result Telesto and Calypso are sometimes referred to as the Tethys Trojans.
     Both moons are relatively white, presumably as a result of ice deposited on their surfaces from the E ring created by ice geysers on Enceladus. They also have unusually smooth surfaces compared to other Saturnian moons. It has been suggested that they are rubble-pile moons, made of loosely stacked bits of ice which when struck by small impactors tend to settle into smoother plains instead of supporting substantial craters. If so, their smooth surfaces might be like the collisional smoothing observed on the asteroid Itokawa.