P51A-2022: Crater Relaxation and Heat Flow on Dione and Tethys

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Authors: Oliver L White, Paul Schenk

Author Institutions: Lunar and Planetary Institute, Houston, TX, USA

O.L. White and P.M. Schenk Lunar and Planetary Institute, 3600 Bay Area Boulevard, Houston, Texas, 77058 Crater relaxation magnitudes on Saturn’s mid-sized icy satellites can provide a record of the history of heat flow across their surfaces [Schenk, 1989]. Precise characterization of the morphologies of these craters is therefore a priority, and Cassini’s orbital tour of the Saturnian system [Matson et al., 2004] has provided near-global stereo coverage for each of the satellites at resolutions better than 1.5 km/px. We have used customized ISIS software developed at LPI to create and process digital elevation models (DEMs) of all of Saturn’s mid-sized icy satellites using Cassini stereo images and photoclinometry. We have so far used these DEMs to obtain depth/diameter plots for a wide range of crater diameters on Rhea and Iapetus, from which we have been able to assess the state of crater relaxation on these satellites [White et al., in preparation]. We are currently in the process of obtaining crater measurements for Dione and Tethys, two satellites that show a more complex crater relaxation history than either Rhea or Iapetus [Jaumann et al., 2009]. Depth/diameter plots for all four satellites are shown in Fig. 1. Relaxation for all crater sizes appears to be negligible on Iapetus, and on Rhea only affects craters above ~100 km diameter, regardless of location on the satellite [White and Schenk, 2011]. On Dione and Tethys, relaxation is less size-dependent and appears to be controlled by location on the satellites, indicating a history of differential heat flow across their surfaces. On Tethys, relaxation and heat flow decreased prior to ~1 Gyr, but continued on Dione for a longer time and with greater intensity [Moore and Schenk, 2007]. We intend to update our measurements for Dione and Tethys with higher quality DEMs obtained from data from recent Cassini flybys. We intend to present depth/diameter plots for Dione and Tethys that are of completeness comparable to our Rhea and Iapetus plots. We will also map relaxation magnitudes of large basins across Dione and Tethys, and consider these measurements alongside crater count-derived ages for the basins in order to assess the thermal histories across these satellites, which may be compared with those derived for Rhea and Iapetus.

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