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 −12   s −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.