Cracks under stress

Abstract

Two modelling studies provide complementary descriptions of how gravitational forces might help to form the plumes of water vapour that spout from cracks in Enceladus, one of Saturn's icy moons. The Cassini flyby of 14 July 2005 revealed plumes of water vapour and ice associated with the 'tiger stripe' features on the surface of Saturn's icy moon Enceladus. Since then the challenge has been to explain the nature of the plumes and the forces driving them. Two papers this week offer an explanation that accounts for both the plume characteristics and the presence of hot spots without the need to assume the existence of near-surface liquid water, a requirement of some previous models. Nimmo et al. identify tidally driven lateral fault motions near the tiger stripes as the most likely drivers of heat and vapour production. And Hurford et al. show that as Enceladus orbits Saturn, the parent planet's tides make the satellite's ice flex. This may cause the tiger stripes to open and close periodically, exposing volatile gases and allowing them to be released.