olsmeister writes "Titan has been a particular focus of attention because of its dense, complex atmosphere, its weather and its lakes and oceans. Now it looks as if Titan is even stranger still. The evidence comes from careful observations of Titan's orbit and rotation. This indicates that Titan has an orbit similar to our Moon's; it always presents the same face toward Saturn and its axis of rotation tilts by about 0.3 degrees. This data allows astronomers to work out Titan's moment of inertia and points to something interesting. The numbers indicate that Titan's moment of inertia can only be explained if it is a solid body that is denser near the surface than it is at its center."