Active eruptions from the south polar region of Saturn's small (~500 km
diameter) moon Enceladus are concentrated along a series of lineaments known as
the `tiger stripes', thought to be partially open fissures that connect to the
liquid water ocean beneath the ice shell. Whereas aspects of the tiger stripes
have been addressed in previous work, no study to date simultaneously explains
why they should be located only at the south pole, why there are multiple
approximately parallel and regularly spaced fractures, and what accounts for
their spacing of ~35 km. Here we propose that secular cooling and the resulting
ice shell thickening and global tensile stresses cause the first fracture to
form at one of the poles, where the ice shell is thinnest due to tidal heating.
The tensile stresses are thereby partially relieved, preventing a similar
failure at the opposite pole. We propose that subsequent activity then
concentrates in the vicinity of the first fracture as the steadily erupted
water ice loads the flanks of the open fissure, causing bending in the
surrounding elastic plate and further tensile failure in bands parallel to the
first fracture, leading to a cascading sequence of parallel fissures until the
conditions no longer permit through-going fractures.Comment: 18 pages, 9 figure
