Kilometer-scale crater size-frequency distributions on Ceres

Abstract

This paper presents an investigation of the size-frequency distribution (SFD) of sub-kilometer-sized projectiles in the Main Belt based on the crater distribution on Ceres. Using image data of 35 m/pixel obtained by the Dawn mission with an onboard Framing Camera during the Low Altitude Mapping Orbit (LAMO), we counted craters having diameter larger than 1 km on the entire surface of Ceres. Based on the crater counting, we investigated the crater size-frequency distribution (CSFD) for the entire surface of Ceres and specifically for floors of 15 named impact craters of various ages. Distinct secondary craters were excluded for derivation of the CSFDs for the 15 crater floors. The CSFDs for the entire surface and those for 8 out of the 15 crater floors show good agreement with the crater production function (PF) for the Lunar Derived Model (LDM), which scales the well-investigated lunar cratering record to the impact environment of Ceres. Although the CSFDs for the other 7 crater floors show somewhat deviations from the PF, the deviations are less likely to show projectile information but are more likely to show the contamination with unidentified secondary craters. Our results indicate that the projectile SFDs on Ceres during 220 Ma – 1.9 Ga are invariably consistent with that found for the Moon. On the other hand, the derived SFDs of sub-kilometer-sized projectiles on Ceres are apparently different from those for the Main Belt Asteroids that have been observed telescopically, which might result from subsurface discontinuity or the Yarkovsky effect.