Double ridges on Europa accommodate some of the missing surface contraction

Crosscutting relationships of tectonic lineaments on Europa record the history of surface deformation. We mapped the displacement and orientation of older features crosscut by two types of lineaments: bands and double ridges. These measurements allow us to determine both the strike-perpendicular and strike-parallel displacement along investigated features. Double ridges record both ridge-perpendicular contraction and expansion, with a mean of 0.160.06 km (needs space) of contraction based on the analysis of 16 double ridges. Bands record expansion, with a mean of 3.330.27km for the six bands analyzed, but with perpendicular displacement less than their apparent morphologic widths of 3-24km. The implied global surface strain for double ridges (including those that expand) and bands is 2.220.76% contraction and 7.603.7% expansion, respectively. Double ridges thus may accommodate part of the surface expansion recorded by bands. Most current models for double ridges do not predict contraction. The models that satisfy the observations for bands are slow-spreading models, cryovolcanism, and folding.