This new picture is based on measurements of Titan's gravity field. The measurements were made by clocking the speed of the NASA-ESA Cassini orbiter with extreme precision—gaguing how many five-thousands of a millimeter the craft traveled per second.

"The ripples of Titan's gravity gently push and pull the spacecraft. By studying the velocity changes we can calculate the gravity," explained study leader Luciano Iess, of Sapienza University of Rome.

Subtle differences in Titan's pull on Cassini suggest that the materials inside the moon are a mix of ice and rock with no clearly defined rocky layers.

Until now, scientists had thought Titan's interior would look a lot like the inside of Jupiter's