Rayed craters on Dione: Implication for the dominant surface alteration process

TL;DR

This study analyzes high-resolution images of Dione's surface to understand the formation, distribution, and short-lived nature of rayed craters, revealing the dominant surface alteration process involves plasma and particle bombardment.

Contribution

It provides the first detailed analysis of rayed craters on Dione, linking their short retention times to surface alteration by plasma and particle implantation.

Findings

29 rayed craters larger than 2 km identified

Rayed crater rays are retained for approximately 1-50 million years

Dark particle implantation erases bright rays, indicating recent surface alteration

Abstract

From recently-acquired, high-resolution images obtained by the Cassini spacecraft, we examine the patterns and spatial distributions of rayed craters on Dione. We identify 29 rayed craters with diameters larger than 2km on Dione's surface. The density of rayed craters and theoretical cratering rates indicate that the retention time for rays on Dione can be approximately 1-50 My. Such a short retention time is interpreted to be due to bombardment of plasma and E-ring particles, as well as implantation of dark particles (presumably the same dark material found on Hyperion, Iapetus, and other saturnian satellites). We also find that when the ray system of Creusa crater was formed, it extended over most of the surface of Dione. Later, the ray system deposited on the trailing hemisphere might have been partially erased, mostly due to implantation of dark particles, which may have also removed other bright ray systems in that region. The pattern of Creusa's ray system implies that the implantation of the dark material occurred more recent than both the age of Creusa crater and the typical retention time for rays on Dione.