Was the Last Event to Fracture Its Surface
Lunar and Planetary Institute | Universities Space Research Association | 2020 Aug 21
Europa’s outer icy shell has completely reoriented itself in one of the last geologic events recorded on its young surface. Europa’s poles are not where they used to be. Cracks in the surface of Jupiter’s icy moon indicate its shell of ice rotated by 70 degrees sometime in the last several million years. In addition to supporting prior evidence for the existence of a subsurface ocean, it also means that the geologic history of Europa’s surface must be reexamined.
New research ... confirms that Europa’s large global scale circular patterns formed during a large reorientation of the its icy outer shell with respect to its spin axis, a process known as true polar wander. This can only happen if the icy shell is uncoupled, or floating free, separated from the rocky core of the planet by a liquid water ocean. ...
Using a combination of global maps from Galileo and Voyager data with improved precision, and detailed topographic data derived from them, a team of scientists ... have correlated large fractures on the surface of Europa with previously identified concentric circular depressions on the surface.
NASA’s Galileo spacecraft orbited Jupiter from 1995 to 2003 and returned hundreds of images of Europa’s surface. Reconstruction of the global map of Europa at 200-meter resolution in color in preparation for a return to Europa revealed that these mysterious fracture systems were part of the circular true polar wander patterns identified previously. Topographic mapping in the highest resolution images of the fractures at 40 meters per pixel show that the fractures are more than 200 meters deep. The fractures cut through all known terrains and thus show that the deformation related to the global reorientation (or true polar wander) event was one of the last events to occur on Europa. These features also imply that the floating ice shell on Europa may have thickened over time. ...
A Very Young Age for True Polar Wander on Europa from
Related Fracturing ~ Paul Schenk, Isamu Matsuyama, Francis Nimmo
- Geophysical Research Letters (online 29 Jul 2020) DOI: 10.1029/2020GL088364