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

Abstract

[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.

Normal faulting on Europa: implications for ice shell properties

“…Schenk and Moore, 1995;Giese et al, 1998;Schenk, 2002). The results have been used in studies of double ridges Hurford et al, 2004), chaos regions (Williams and Greeley, 1998;Figueredo et al, 2002;Schenk and Pappalardo, 2004) and bands (Prockter et al, 2002;Nimmo et al, 2003a).…”

“…A considerable amount of work has been done on both the fracture orientation (Kattenhorn, 2002;Greenberg et al, 2003;Spaun et al, 2003) and the direction and amount of motion (Hoppa et al, 2000;Prockter et al, 2002;Michalski and Greeley, 2002;Sarid et al 2002;Schulson, 2002;Patterson et al, 2004). In the absence of altimetry data, photoclinometry (PC) or stereo techniques have been used to obtain icy satellite topography (e.g.…”

Seeking Europa's Ocean

“…Typical double ridges on Europa's surface. from below, which is then fractured as extension continues (Prockter and Patterson, 2009). This model suggests that bands are icy analogs to the spreading centers that exist on Earth's rocky ocean floors, with new lithospheric ice created along an axial trough and shunted laterally then commonly faulted (Prockter et al, 2002).…”

“…Formation of these ridges is probably related to the rise of water or warm ice along fractures (Kattenhorn and Hurford, 2009;Prockter and Patterson, 2009). A geophysically plausible model for their formation suggests that ridges are produced as the opposing sides of faults grind back-and-forth against each other as Europa orbits, generating heat akin to rubbing your hands together.…”

“…from below, which is then fractured as extension continues (Prockter and Patterson, 2009). This model suggests that bands are icy analogs to the spreading centers that exist on Earth's rocky ocean floors, with new lithospheric ice created along an axial trough and shunted laterally then commonly faulted (Prockter et al, 2002). Unlike Earth's plate tectonics, however, there are no subduction zones identified on Europa, and only rare examples of folding have been identified (Prockter and Pappalardo, 2000), so the compensation of band extension remains an unresolved issue.…”