Craterization and age of Saturns small satellites.

ZANARDI, M.; ROSSIGNOLI, N. L.; DI SISTO R.P.

Congreso; Segunda Reunión Binacional AAA-SOCHIAS,; 2018

Craters generated by collisions on the Solar System objects represent the most distinctive marks on their surfaces, allowing us to peek into their past to discover their history and evolution. Recent missions to theSolar System objects have enabled us to study these structures in high detail and to pose new questions about the physical, dynamical, chemical and even biological processes that take place in them. Saturn's satellite system is very diverse: it includes the Solar System's second largest moon, Titan, a variety of medium size satellites such as Enceladus and its plumes that feed the E ring, the irregular satellites, and the smaller satellites with their peculiar shapes and characteristics. In this work we study Saturn's smallest satellites: those whose orbits are related to the A ring, the coorbitals Janus and Epimetheus, the tiny satellites that orbit embedded in arcs between Mimas and Enceladus, Dione and Tethys' trojans, and the highly cratered Hyperion, Saturn's largest irregular satellite. Using a theoretical model we calculate the impact distribution generated by Centaurs and the consequent crater production on the dierent satellites. Then we compare our results with the observations made by the Cassini and the Voyager missions. This enables us to study the physical consequences of crater production on these satellites' surfaces and to establish restrictions on both their origin and formation. Our results suggest that among this group of `small satellites', the largest ones could be primordial, although highly cratered and featuring very large impact craters. On the other hand, the smallest ones could not have survived the collisions by Centaurs in the present conguration of the Solar System. This implies that during the age of the Solar System, very small satellites could have orbit Saturn at similar distances, but they would have suered catastrophic fragmentations, leaving behind only a primordial nucleus from which a new satellite could have re-accreted. This is in agreement with Saturn'ssatellite formation theories (e.g Crida and Charnoz, 2012. Science, 338, 1196) and with the observations made by Cassini, that show that satellites Pan, Atlas and Daphnis have undergone accretion processes of material from the A ring (Charnoz et al. 2007. Science, 318, 1622). These satellites have an elongated shape with ecuatorial ridges made of recently accreted ring material (Porco et al. 2007, Science, 318, 1602).