CREATING ICE FISSURE ANALOGUES TO MODEL THE CRYOVOLCANIC PROCESSES AND TIDAL FRACTURING OF SATURN'S SATELLITE ENCELADUS

Enceladus is a small, icy body orbiting within the E ring in Saturn's moon system—a minor ring orbiting the planet with a composition similar to the eruptive materials of the satellite. Once thought to be too small for activity, recent data and images taken by NASA's Cassini probe orbiting Saturn have revealed this is not the case. Enceladus has exhibited significant recent resurfacing, extensional and shearing features in the form of 130 kilometer linear cracks, and also active geyser plumes erupting cryovolcanic material in the form of water vapor and ice. The heat source of the activity on Enceladus is caused by tidal forces, rather than radioactive decay heating, which drives the volcanism of larger planets such as Earth. The eccentric, elliptical orbit of Enceladus around Saturn, and gravitational effects of another nearby body, Dione, alternately expand and contract the satellite. This change in size causes cracks in the surface, which are heated and erupt. The eruption plume observed by Cassini in 2005 showed a composition of primarily water (91%), with lesser amounts of nitrogen (4%), carbon dioxide (3.2%), and methane (1.6%). To show some of the effects of tidal gravitational forces on Enceladus and other icy satellites, we model the expansion and contraction of the body to create fractures using small balloons and domed objects like “whoopee cushions” and freezing ice layers over their surfaces. These models are then stretched by adding air, simulating tidal expansion. The ice layer on top undergoes brittle deformation by forming cracks and fractures. Ongoing experiments employ more exact scales for the ratio of the icy surface to interior, replicating possible subsurface water movement, and employing other methods of surface expansion.