Model constraints on the opening rates of bands on Europa

A mid-ocean-ridge spreading analog is used to constrain the opening rates and brittle-ductile transition depths for two axisymmetric ridged bands on Europa. Estimates of brittle-ductile transition depth based on the morphologies of Yelland and Ino Lineae are combined with a conductive cooling model based on a mid-ocean ridge analog to estimate the opening rates and active lifetimes of the bands. This model limits local strain rates to ∼10−15-10−12s−1, opening rates to 0.2-40 mm yr−1, and active lifetimes of the bands to 0.1-30 Myr. If the observed structures in the outer portions of ridged bands are indeed normal faults, the estimated range for the tensile strength of ice on Europa is 0.4-2 MPa, consistent with nonsynchronous rotation as the dominant driving mechanism for band opening.