Europa: Stratigraphy and geological history of the anti-Jovian region from Galileo E14 solid-state imaging data

Abstract

A tidal bulge and associated deformation are predicted to occur in Europa's anti-Jovian region. Voyager data showed polygonal, low-albedo bands in this region. It was demonstrated that when the low-albedo material comprising these bands was removed, the margins could be reconstructed, suggesting that fracturing and lateral separation has occurred. Higher-resolution Galileo images of a 300,000 km2 portion of the anti-Jovian region permit recognition and mapping of a variety of features and documentation of the geological history. We identify background ridged plains, several distinctive types of bands and ridges, lenticulae, and regions of chaotic terrain. These images are at relatively low incidence angles; thus albedo variations predominate over topography. This presents a challenge to morphologically based mapping but does not preclude development of a regional stratigraphy. Stratigraphic relationships show that dark bands crosscut the bright ridged plains and are themselves disrupted by lenticulae and chaos, suggesting a geological history beginning with background ridged plains, followed by a period dominated by band formation, with the most recent history predominantly characterized by formation of lenticulae and chaos. The paucity of impact craters in this region indicates that the entire sequence of units is geologically recent. Copyright 1999 by the American Geophysical Union.