"Wavy" Lineaments on Europa

Thursday, February 24, 4:10pm, 1 LeConte

Bob Pappalardo

Previous studies have shown that global-scale lineament patterns on Europa can be explained by accumulation of tensile stress from slow nonsynchronous rotation (NSR) of the satellite's icy shell, while the cycloidal forms of other Europan lineaments can be explained if fractures propagate through a diurnally changing tensile stress field. New modelling of combined NSR and diurnal stresses shows that resultant propagating fractures can be "wavy" in planform, for NSR stress accumulated over ~2 to 8 of ice shell rotation and fracture propagation speeds of ~1 to 3 m/s. Thus, the variety of Europa's observed lineaments from cycloidal, to wavy, to arcuate can be produced by accumulation of NSR stress relative to the diurnal stress field. Fitting individual Europan lineaments to model results can constrain the combined NSR plus diurnal stress field at the time of fracture. The apparent varying proportions of these stress mechanisms in creating lineaments across Europa's surface is plausibly related to decreasing NSR stress over time.