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

A tidal bulge and associated deformation are predicted to occur in Europa's anti-Jovian region. Voyager data showed polygonal, low-albedo bands in thi s region. It was demonstrated that when the low-albedo material comprising these bands was removed, the margins could be re constructed, suggesting th at fracturing and lateral separation has occurred. Higher-resolution Galile o images of a 300,000 km(2) portion of the anti-Jovian region permit recogn ition and mapping of a variety of features and documentation of the geologi cal history. We identify background ridged plains, several distinctive type s of bands and ridges, lenticulae, and regions of chaotic terrain. These im ages are at relatively low incidence angles; thus albedo variations predomi nate over topography. This presents a challenge to morphologically based ma pping but does not preclude development of a regional stratigraphy. Stratig raphic relationships show that dark bands crosscut the bright ridged plains and are themselves disrupted by lenticulae and chaos, suggesting a geologi cal history beginning with background ridged plains, followed by a period d ominated by band formation, with the most recent history predominantly char acterized by formation of lenticulae and chaos. The paucity of impact crate rs in this region indicates that the entire sequence of units is geological ly recent.