Hyperion is one of the smaller moons of Saturn. It has a pock-marked body and is the largest, irregularly-shaped satellite ever observed.
Hyperion might have had a major collision which blew part of the moon away. Its eccentric orbit makes it subject to gravitational forces from Saturn which have set it tumbling out of control. The moon's rotational period is not constant and varies from one orbit to the next.
The irregular shape of Hyperion and the amount of bombardment by meteors makes it appear to be the oldest surface in the Saturn system.