[X] My Assistant

[belleraphon1]

Titan T28 mission description is now available. Note grountracks displayed on pp 9-10.
http://saturn.jpl.nasa.gov/multimedia/prod...description.pdf

[Juramike]

The Dancing Monkey feature located in the bright temperate highland area N of Adiri (approx location [30N, 210W]) looks very much like a cycloid crack pattern as seen on Europa.
Here are is an image of the Dancing Monkey feature (clipped from the CICLOPS website in the Looking Ahead Rev 47 post). And here is an image of a similarly complex patterned area on Europa.



It is thought that the cycloids are generated by diurnal tides. (Europa orbits Jupiter every 3.55 days). Each arc is generated in one orbit due to changing and rotating tidal forces. The area on Titan and the area imaged on Europa are in almost the same tidal force environments (same longitude, almost exact opposite latitude). [Fun fact: (0N,0W) is the subprimary point for rotationally locked moons.] See this post for diagram showing Titan’s tidal forces and this post showing where the forces in Titan are strongest.


Cycloid cracks are now thought to result from rotating tensile and shear stresses (Marshall and Kattenhorn Icarus 177 (2005) 341-366. “A revised model for cycloid growth mechanics on Europa: Evidence from surface morphologies and geometries” HTML (text-only no pictures - freely available here (A earlier work describing strike-slip faults on Europa is available freely here). A diagram of the cycloid growth model proposed by Marshall and Kattenhorn is shown below:



At a certain point, the tensile strength of the crust (ice) breaks and a crack forms and propagates. If the forces rotate faster than the crack propogates, the crack will try to form an arc. But as the forces rotate faster, they set up a shear as the tidal pull yanks the material on one side of the crack. The crack then begins to behave as a slip fault. Eventually the tensile force decreases, the crack stops propogating. But the forces keep rotating and eventually set up a shear in the old crack, and a tensile stress in the terminus. The shear forms a “tailcrack” and the crack propogates again. This makes a line with a series of arcs hopping across the surface.

From the article, I got the impression that faults and cycloid cracks on Europa might be two flavors of the same thing.

Also, cycloid cracks have recently been observed on Enceladus’s south pole: Hurford et al. LPS XXXVIII (2007) Abstract 1844. “A cycloid-like rift near Enceladus’ South Pole: Europa-style Production by Tidal Stress.”. Abstract freely available here.

-Mike