What's inside Titan?

Caption NASA:"This artist's illustration shows the likely interior structure of Saturn's moon Titan, as deduced from gravity field data collected by the Cassini Spacecraft. The investigation by Cassini's radio science team suggests that Titan's interior is a cool mix of ice studded with rock, though the outermost 500 Km (approx. 300 miles) appear to be ice essentially devoid of any rock.
Many planets and moons, including the Earth, evolve into a body with a clearly distinct rocky core. This radio science investigation suggests Titan's interior, cool and sluggish, failed to allow the interior to separate into completely differentiated layers of ice and rock.

In addition to the Hazy Surface of Titan (yellow), the layers in the cutaway show an ice layer starting near the Surface (light gray), an internal ocean hypothesized from other Cassini data (blue), another layer of ice (light gray) and the mix of rock and ice in the interior (dark gray). In the background are the Cassini Spacecraft and Saturn, not to scale".