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| Relaxation and the Formation of Prominent Central Peaks in Large Craters on the Icy Satellites of Saturn |
| Presentation Time: Monday, 4:10 p.m. - 4:20 p.m. |
Andrew J. Dombard1, V. J. Bray2, G. S. Collins2, P. M. Schenk3, E. P. Turtle1
1Johns Hopkins Univ. Applied Physics Laboratory, 2Imperial College London, United Kingdom, 3Lunar and Planetary Institute. |
| Presentation Number: 11.05 |
| Several of the icy satellites of Saturn (e.g., Dione, Mimas, Tethys) possess large craters (greater than ~100 km in diameter) with very prominent central peaks. These peaks often exceed the elevation of the background terrain and rise above the crater rim. It has been thought that these peaks denote something peculiar associated with large crater formation on mid-size icy satellites, but we show that these peaks are instead the product of post-impact relaxation of the crater topography. Unlike previous relaxation studies, ours is the first to include remnant heat from the impact. We constrain the post-impact temperature field beneath a crater using hydrocode simulations. This temperature field is then used as input into a thermomechanical finite-element simulation, where we not only track the relaxing topography but also the diffusing thermal anomaly. Because the post-impact temperatures are highest in the central portion of the crater floor, a transient phase of rapid relaxation as the thermal anomaly dissipates results in concentrated floor-uplift, thereby explaining these ginormous central peaks. The background heat flow needs to be high enough to accommodate this deformation, which allows estimation of the thermal state of these satellites when these craters formed. Similarly extreme peaks are not found on the icy Galilean satellites of Jupiter because central peaks in large craters are replaced by other complex crater morphologies such as central pits. |
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