An analysis of gravity and topography data from Saturn’s largest moon, Titan, has revealed that it’s ice shell is rigid and the small topographic features on it’s surface are linked with large roots extending into the underlying ocean.
Led by planetary scientists Douglas Hemingway and Francis Nimmo at the University of California, Santa Cruz, the study used new data from NASA’s Cassini spacecraft.
Nimmo, a professor of Earth and planetary sciences at UC Santa Cruz, said that on Titan, when you fly over a mountain the gravity gets lower, which is a very odd observation.
To explain that observation, the researchers developed a model in which each bump in the topography on the surface of Titan is offset by a deeper “root” big enough to overwhelm the gravitational effect of the bump on the surface.
The root is like an iceberg extending below the ice shell into the ocean underneath it.
Nimmo explained that because ice is lower density than water, you get less gravity when you have a big chunk of ice there than when you have water.
Lead author Hemingway, a doctoral candidate in planetary geophysics at UCSC, said that if large roots are the reason for the negative correlation, it means that Titan’s ice shell must have a very thick rigid layer.
The researchers calculated that, in this model, Titan’s ice shell would have to have a rigid layer at least 40 kilometers thick and found that hundreds of meters of surface erosion and deposition are needed to account for the observed imbalance between the large roots and small surface topography.
The study has been published in the journal Nature.