A Very Young Age for True Polar Wander on Europa From Related Fracturing. Issue 17 (2nd September 2020)

• Record Type: Journal Article
• Authors: Schenk, Paul; Matsuyama, Isamu; Nimmo, Francis
• Is Part Of: Geophysical research letters. Volume 47:Issue 17(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-09-02
• Subjects: Europa -- reorientation -- tectonics -- ice -- polar wander; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2020GL088364
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: 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. Plain Language Summary: The large icy ocean world of Europa has a very young surface that has been highly deformed. Recent evidence for "polar wander, " or reorientation of the floating outer ice shell away from its original orientation, has been confirmed by the recognition that long fissures are part of the polar wander tectonic pattern and are among the youngest features on the planet. This means that polar wander occurred very recently and that older features are no longer in their original locations and will require a complete reassessment of Europa's tectonic history. Key Points: Fractures on Europa confirm that true polar wander (reorientation) of the outer icy shell occurred The fractures confirming true polar wander crosscut all known terrains and confirm that polar wander was a very recent event All older features on Europa are no longer in their original orientations and stress models must be reevaluated