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A. J. Dombard (Johns Hopkins U. Applied Physics Lab.), W. B. McKinnon (Washington University)
Potential contractional folds on Jupiter's icy moon Europa have been identified. The best example is at the extensional band Astypalaea Linea, where a series of subtle topographic undulations, 25 km in wavelength, possess parasitic tectonic features that support a folding origin. A scenario has been qualitatively proposed, whereby folds form via unstable contraction of the icy lithosphere, compensate for extension elsewhere on Europa, and then subsequently relax. Here, we quantitatively address this scenario, applying a model for viscous-plastic buckling of planetary lithospheres and finite element simulations of topographic relaxation. Our results suggest that the lithosphere of Europa could indeed be unstable, but the low required surface temperatures limit fold formation to higher latitudes, and the high required driving stresses (~9-10 MPa) are difficult to achieve on the satellite. High thermal gradients are indicated, which imply heat flows near 100 mW m-2. In addition, topographic relaxation progresses so slowly even at these heat flows that it is not a viable mechanism to eliminate such features over the age of Europa's surface. Given the paucity of identified folds, we conclude that the necessary conditions for their formation are rare and that lithospheric folding is a very minor mechanism for compensating the large amounts of extension seen elsewhere on Europa. AJD was partially funded by NASA Grant NAG5-13243 to Roger Phillips and by indirect funds from the Johns Hopkins University Applied Physics Laboratory; WBM was supported by NASA Planetary Geology and Geophysics grants NAG5-3657 and NAG5-11517 and Jupiter Systems Data Analysis Program Grant NAG5-8899.
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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.