EXPLORING TIDAL STRESSES TO ANALYZE EUROPA'S INNER AND OUTER TURMOIL

The geological history of Jupiter’s moon Europa is fascinating due to its lack of impact craters (suggesting a relatively young surface), an ocean water layer, and potential plume activity. The presence of plumes, if confirmed, would be significant for future astrobiological research. It would provide strong evidence of liquid water and the possibility of characterizing the composition of the subsurface ocean. Water ice is abundant in the outer solar system, especially on the moons of gas giants. This contrasts with the inner solar system, where silicate rock dominates. The rheology of ice mimics that of silicates, but there are key differences (water ice is less dense than liquid water—the opposite of most silicates—and silicates have much higher melting points) that may lead to different geological processes. Here we model tidal stresses on Europa using SatStressGUI. This model assumes a viscoelastic body with four layers: an upper and a lower crust/shell, a core, and a subsurface ocean. SatStressGUI allows users to simulate the effects of: diurnal tides, nonsynchronous rotation rates (NSR), obliquity, ice-shell volume changes, polar wandering, despinning, and orbital recession/decay. As a demonstration of recent updates to the program, we calculate stresses and Love numbers for diurnal tidal effects and NSR on Europa. These calculations are compared to observations of potential plume activity, such as those detected by the Galileo spacecraft and the Hubble Space Telescope. We then determine Europa’s orbital position and calculate the orientation of principal stresses acting on linear features on the USGS geologic map of Europa. This allows us to determine the time-variable conditions that may affect the likelihood of a plume occurring. For example, if a fracture was found to be in tension around the time and place a plume was observed, it is more likely that it was the source of activity.