This spongy-looking object is Hyperion, one of Saturn's many moons. Hyperion has a deeply cratered surface caused by impacts. It also has dark material that absorbs heat from the sun and melts into the moon's surface. Scientists think the moon may have an unusually low density for such a large object, giving it weak surface gravity and a tendency to be very porous.
To learn more about this oddly shaped moon imaged by the Cassini spacecraft, visit http://solarsystem.nasa.gov/planets/profile.cfm?Object=Sat_Hyperion