Science Seminars

Smashing Saturn; an Analysis of the Impact Crater Record on Tethys and Dione

Speaker: Sierra Ferguson (SWRI)
Date: Thursday, Nov 04, 2021
Time: 4:00 PM
Location: Zoom

Seminar Abstract:

A remaining question after the conclusion of the Cassini mission is “How old are the inner satellites and how did have they been modified?” This question is of critical importance for the refinement of how solar systems and giant planet systems form and evolve. Determining the ages of the satellites also has implications for the durations of subsurface oceans that may have once been present under the ice shells of several of these mid-sized moons. One of the most direct ways to test the ages of a planet’s surface is through the use of impact craters and analysis of their sources. Here we utilize images from the Cassini Imaging Science Subsystem (ISS) to analyze craters on two of the mid-sized moons of Saturn; Tethys and Dione. Elliptical craters provide another means of assessing the bombardment environment around Saturn as they record the primary direction of the object that created the crater upon impact on the surface. We have mapped these craters on Tethys and Dione to analyze the global distributions of these craters and their orientations. Across both satellites, we find that in the equatorial regions between 30° N/S in latitude, the orientations of the elliptical craters are predominantly oriented East/West. One interpretation of this signal is that these craters were formed by a local planetocentric source as it would likely lie within the same orbital plane as the satellites. In addition to the elliptical craters, we mapped at a regional scale (~200 m/pix) across both surfaces to investigate potential regional differences in the cratering. Neither of the previously predicted production functions for the Outer Planets fit perfectly with the observations we have in the Saturn system. We interpret this difference to be indicative of a local planetocentric source that has had a large impact on the observed crater record.