Morphology of Europan bands at high resolution: A mid-ocean ridge-type rift mechanism

[1] We utilize imaging data from the Galileo spacecraft to investigate band formation on one of Jupiter's moons, Europa. Bands are polygonal features first observed in Voyager data close to Europa's anti-Jovian point and represent areas where preexisting terrain has been pulled apart, allowing new material to move up into the gap. We examine the detailed morphology of several bands imaged at different resolutions and lighting geometries. We identify several distinct morphological characteristics, including central troughs, hummocky textures, and ridge and trough terrains, some of which are common among the bands studied. In many cases, bands have initiated along segments of one or more preexisting double ridges, ubiquitous within Europa's ridged plains. Distinctive morphological features and high standing topography imply that the bands formed from compositionally or thermally buoyant ice, rather than liquid water. Comparisons between Europan band morphologies and features found on terrestrial mid-ocean ridges reveal several similarities, including axial troughs, subcircular hummocks, normal faults, and indications of symmetrical spreading. We conclude that terrestrial mid-ocean ridge rifting is a good analogy for Europan band formation. If a terrestrial seafloor-spreading model is applicable to Europan bands, we speculate that band morphologies might be related to the relative rate of spreading of each band. Bands may have contributed significantly to the resurfacing of Europa. Europan bands we examine predate (but do not postdate) lenticulae and related features, implying that the style of resurfacing on Europa has changed over recent geological time in these regions.