FORMATION OF CYCLOIDAL FEATURES ON EUROPA.

Gregory V. Hoppa, B. Randall Tufts, Richard Greenberg, Paul E. Geissler, LPL, University of Arizona, Tucson, AZ 85721-0092 (hoppa@lpl.arizona.edu).


Science Vol 285, 17 September 1999, p. 1899-1902.

Cycloidal ridges near Europa's south pole as viewed by the Voyager spacecraft (58° S, 166° W).

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Animation of the Formation of a Cycloidal Feature. This animation shows a crack propagating westward in the southern hemisphere of Europa. The arrows represent the changing amplitude and orientation of the tensile stress due to tides.

Animation of the Formation of a Cycloidal Feature. This animation shows a crack propagating eastward in the southern hemisphere of Europa. The arrows represent the changing amplitude and orientation of the tensile stress due to tides.

Cycloidal double ridges viewed in the northern hemisphere of Europa (60° N, 80° W).

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Extensional wedge-shaped bands (shown as darker features) (15° S, 195° W) were probably initiated as cycloidal cracks.


Model of cycloidal crack formation on Europa. The arrows represent the amplitude and orientation of the tensile stress; the numbers below the arrows indicate the hours of the orbit. During the first orbit, cracking is initiated 33 hours after perijove. As propagation of the crack continues, the orientation of the tensile stress vector changes, causing the crackto change course. At 71 hours into the orbit, tension decreases to a point where crack propagation is no longer possible. The process repeats itself on subsequent orbits, making the characteristic cycloidal chain.



Please send comments to: hoppa@pirl.lpl.arizona.edu