Modeling Surface Stresses on Europa

Introduction: Modeling of the surface stresses on Europa has been performed to date, considering tidal, nonsynchronous, and polar wander sources of stress [3-6]. The results of such models can be used to match lineament orientation with the candidate stress patterns. Moreover, stratigraphic analysis can be used in combination with stress modeling to infer the evolution of Europa’s surface back through time [9,12]. We are creating a surface stress model for Europa (in MATLAB) that will facilitate comparison of principal stresses to lineament orientation, and which will be available in the public domain. Modeling Surface Stresses: Nonsynchronous rotation and diurnal stresses contribute to a stress pattern that affects the surface of Europa, each on a very different time scale. Over the 85-hour orbital period, the diurnal stress pattern acts on the surface, with a maximum magnitude of ~40 kPa [21]. The nonsynchronous stress pattern sweeps over the surface due to the faster rotation of the icy shell as compared to the tidally locked interior of the moon, and occurs with a period of >10,000 years [21]. Polar wander (reorientation of the icy shell with respect to the axis of rotation) may contribute to the surface stress pattern on Europa [4]. When added, the resulting stress pattern can be used to predict the orientations of lineaments, as well as the regions within which faulting should occur [e.g. 3]. Mechanisms and timescales for reorientation of the icy shell of Europa have been considered using various geophysical models [16-21]. One approach toward understanding the surface stresses on Europa is to determine the stress difference induced by a change in flattening [e.g. 4]. We employ a different method, based on calculating the surface stresses from the Love numbers. Stressing the surface of a planetary body can be modeled by calculating the vector components of displacement s at the surface, which are functions of the potential V: