Episodic Plate Tectonics on Europa: Evidence for Widespread Patches of
Mobile-lid Behavior in the Antijovian Hemisphere
Abstract
A nearly pole-to-pole survey near 140°E longitude on Europa revealed
many areas that exhibit past lateral surface motions, and these areas
were examined to determine whether the motions can be described by
systems of rigid plates moving across Europa’s surface. Three areas
showing plate-like behavior were examined in detail to determine the
sequence of events that deformed the surface. All three areas were
reconstructed to reveal the original pre-plate motion surfaces by
performing multi-stage rotations of plates in spherical coordinates.
Several motions observed along single plate boundaries were also noted
in previous works, but this work links together isolated observations of
lateral offsets into integrated systems of moving plates. Not all of the
surveyed surface could be described by systems of rigid plates. There is
evidence that the plate motions did not all happen at the same time, and
that they are not happening today. We conclude that plate tectonic-like
behavior on Europa occurs episodically, in limited regions, with less
than 100 km of lateral motion accommodated along any particular boundary
before plate motions cease. Europa may represent a world perched on the
theoretical boundary between stagnant and mobile lid convective
behavior, or it may represent an additional example of the wide
variations in possible planetary convective regimes. Differences in
observed strike-slip sense and plate rotation directions between the
northern and southern hemispheres indicate that tidal forces may
influence plate motions.