An exceptionally high standing ridge on Enceladus

Abstract

Cassini stereo-derived topography reveals an exceptionally high-standing sawtooth-shaped ridge in Enceladus’ Samarkand Sulcus. Over a length of 100 km and of a width of 10 km, it reaches elevations of up to 1750 m, which makes it the highest ridge observed on Enceladus so far. Flank slopes reach 40°. The morphology of the ridge suggests that it formed first by rift flank-uplift caused by extension, but sinistral shear and compression later modified the shape. This modification has in particular emplaced small-scale fragments sticking out of the surface and creating a (previously enigmatic) pattern of black spots on the sun facing side of the ridge. Modelling of uplift related lithospheric flexure yields an effective elastic thickness (Te) of 0.36 km (E=1 GPa) at the time of formation, similar to results obtained in Harran Sulcus [1]. Considering the ridge as a load on the lithosphere at present-day, we obtain a lower limit on Te of 1.5 km. Within an asteroid/comet based impact chronology the ridge is 3.6/0.7 Gy old.