EXPOSING THE ICY MOON’S SECRET AGE USING MODEL CRATER CHRONOLOGY OF THE OUTER SOLAR SYSTEM
Seminars
Are Saturn's regular satellites young or old? And how old are Enceladus' plains? To answer these questions, we computed model surface ages of the most heavily cratered terrains on Saturn's regular icy satellites using new high-resolution outer Solar System evolution simulations and coupled with improved estimates of the trans-Neptunian objects populations. The output of the simulations allowed us to construct a model impact chronology onto Saturn which automatically applies to its regular satellites. We used crater densities and our impact chronology onto Saturn to construct model impact-crater isochrones, i.e., the scaling of the satellite crater production function with time. The surface ages derived for the cratered plains on Mimas, Enceladus, Tethys, Dione and Rhea range from 4.1 Ga to 4.4 Ga, with the surfaces of Mimas and Enceladus roughly 250 Myr younger than those of the outer three satellites. Uncertainties in these ages are within 300 Myr.
The calculated model surface ages of these satellites are consistent over as much as two orders of magnitude in the observed crater diameter. This work supports the idea that Saturn's regular satellites are ancient and has implications for their formation and their tidal evolution.
Additional information: Prof Man Hoi Lee, mhlee@hku.hk