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Examination of elliptical craters on Saturn’s moons Tethys and Dione constrain their ages and origin

Presentation #106.02 in the session “Impacts, Collisions, and Disruptions”.

Published onJun 01, 2021
Examination of elliptical craters on Saturn’s moons Tethys and Dione constrain their ages and origin

Elliptical craters are a useful morphology of crater for examining the impact source populations. These craters are formed at shallow impact angles (i ~ ≤ 15°) and thus record the trajectories of the source impactor (Bottke et al., 2000). Elliptical craters have been utilized in other studies to better characterize the impactor population of Mars and changes in its obliquity (Bottke et al., 2000; Holo et al., 2018). We’ve mapped elliptical craters in regional studies on Saturn’s moons Tethys (Ferguson et al., 2020) and Dione. To distinguish between a heliocentric and planetocentric source for these elliptical craters, we hypothesize that craters formed by planetocentric debris would be oriented in a distinct E/W direction whereas the heliocentric debris would impact across any angle in an isotropic pattern (Zahnle et al., 1999). Across both moons, we found that elliptical craters are clustered in orientation and latitude in ways that favor a planetocentric source of the debris that is most prominent near the equator. We, thus, completed a regional study on a high latitude area of Tethys to derive a surface age for an area that had likely been more dominated by heliocentric impactors than planetocentric. We present results highlighting our global survey of elliptical craters across the base maps of Tethys and Dione, where we find a preferential clustering of elliptical craters orientated E/W in the mid latitudes (30° S to 30° N). At higher latitudes on both moons, the orientations become more spread out, suggesting a heliocentric source. We propose the source of these E/W oriented elliptical craters to be from a transient debris disk that was located in the inner Saturnian system for a brief time. We discuss implications for the ages of Tethys and Dione and their formation.

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