JUPITER’S MOON EUROPA: NEW INSIGHTS INTO GOBAL RESURFACING PROCESSES AND PLANETARY ICE TECTONICS FROM PHYSICAL EXPERIMENTS (Invited Presentation)

Jupiter’s moon Europa is a differentiated planetary body comprised of a metallic core, a silicate mantle, and an outer shell of H2O. This shell can be further subdivided into an icy surface shell and a liquid subsurface ocean [1]. Europa has one of the youngest geologic surfaces in our solar system with an age of 40 - 90 Ma [2], implying an intense history of resurfacing. Recently, evidence for potential subduction zones has been discovered on Europa at which the brittle, conductive surface ice layer is pushed and subsumed into the warmer, convecting subsurface ice [3]. This large-scale process, analogous to terrestrial subduction, could be responsible for recycling most of Europa’s surface [3]. However, basic physical parameters of subduction initiation on Europa are not well understood.

In this study, we aim to understand the process and the conditions that could lead to the initiation of subduction on Europa by using physical analogue wax experiments. Specifically, we investigate what role conductive layer thickness, deformation rate, and pre-existing zone of weakness orientation play in the initiation of subduction. The wax is heated from below and cooled from above, similar to [4]. Our results indicate that subduction can be initiated over a broad range of surface thicknesses and deformation rates above a minimum conductive layer thickness, but is strongly dependent on the orientation of the pre-existing zones of weakness. Below a critical conductive layer thickness, the layer experiences folding and warping during shortening and results in a previously undescribed process we call ductile rollback. During ductile rollback, surface material is pushed into the warmer subsurface at a pre-existing zone of weakness with increasing boundary displacement. Thus, based on the results of our experiments, subduction and ductile roll back are physically possible mechanisms that could play a critical role in resurfacing Europa throughout its geologic history.

References: [1] Pappalardo et al. (1999) J. Geophys. Res. Planets, 104, 24015-24055. [2] Bierhaus et al. (2009) Europa, Ed. Pappalardo, McKinnon, Khurana; University of Arizona Press, Tucson, 2009. ISBN: 9780816528448, p. 161, 161. [3] Kattenhorn and Prockter (2014) Nat. GeoSci., 7, 762-767. [4] Manga and Sinton (2004) J. Geophys. Res. Planets, 109, E9.