Disruption of Saturn's ring particles by thermal stress

TL;DR

This paper proposes that thermal stress from temperature variations can fragment large ring particles and boulders on icy satellites, explaining observed size distributions in Saturn's rings and other icy bodies.

Contribution

The study introduces thermal stress as a key process in breaking down large particles in planetary rings and icy satellite surfaces, a novel explanation for their size distribution.

Findings

Thermal stress can grind particles larger than 10-20 m in Saturn's rings.

Fragmentation by thermal stress may explain the absence of large boulders on icy satellites.

Thermal stress effects are significant in the evolution of icy satellite surfaces, especially in geologically inactive regions.

Abstract

Spacecraft and ground-based observations show that the main rings of Saturn lack particles larger than 10 m. Tidal or collisional destruction of satellites/comets have been proposed as the origin of the main rings; however, Saturn's tide alone cannot grind km-sized fragments into submeter-sized particles because of the high mechanical strength of water ice and rock. The question arises as to why such large particles are not left in the current ring. It is known that thermal stress induced by diurnal and seasonal temperature variations can cause weathering and fragmentation of boulders and contribute to dust and regolith production on the Moon and terrestrial planets, and then such thermal stress can break particles larger than a critical radius while cannot smaller than the critical radius. In this study, we examined the role of thermal stress acting on Saturn's ring particles. We found that thermal stress can grind porous ring particles larger than 10-20 m, which explains the lack of particles larger than 10 m in Saturn's ring. Also, fragmentation by thermal stress can be adoptable for the Epsilon rings of Uranus. Furthermore, thermal stress caused by diurnal or seasonal temperature variation acting on boulders on surfaces of icy satellites and asteroids may play an important role in the evolution of their sizes. Our calculations explain the lack of boulders on icy satellites, except in the geologically active provinces such as the tiger stripes of Enceladus, where boulders are supplied by recent geological activity. We predict that future observations can find numerous boulders around Europa's geologically active cracks.