En echelon fissures 100–300 km long on Europa are found to be concentric and external to arcuate troughs previously attributed to true polar wander (TPW) of Europa's ice shell, strengthening the case for TPW. Fissures are composed of parallel faults distributed over 10-to-20-km-wide zones, with deformation focused in a main fissure 1–2 km wide and up to 200 m deep. Fissures crosscut all known terrains, including (apparently) ejecta of bright ray crater Manannan, establishing that fissures and by inference TPW are among the most recent geologic events on Europa. Very late ~70° of TPW shell rotation requires that most observed structures on Europa are not in their original configuration with respect to other stress regimes, requiring complete reanalysis of Europa's strain history. If reorientation happened recently, we predict that any crater distribution asymmetries and shell thickness variations measured by Europa Clipper will be offset from expected equilibrium patterns.
- polar wander
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)