Eruptions arising from tidally controlled periodic openings of rifts on Enceladus

Abstract

In 2005, plumes were detected near the south polar region of Enceladus, a small icy satellite of Saturn. Observations of the south pole revealed large rifts in the crust, informally called 'tiger stripes', which exhibit higher temperatures than the surrounding terrain and are probably sources of the observed eruptions. Models of the ultimate interior source for the eruptions are under consideration. Other models of an expanding plume require eruptions from discrete sources, as well as less voluminous eruptions from a more extended source, to match the observations. No physical mechanism that matches the observations has been identified to control these eruptions. Here we report a mechanism in which temporal variations in tidal stress open and close the tiger-stripe rifts, governing the timing of eruptions. During each orbit, every portion of each tiger stripe rift spends about half the time in tension, which allows the rift to open, exposing volatiles, and allowing eruptions. In a complementary process, periodic shear stress along the rifts also generates heat along their lengths, which has the capacity to enhance eruptions. Plume activity is expected to vary periodically, affecting the injection of material into Saturn's E ring and its formation, evolution and structure. Moreover, the stresses controlling eruptions imply that Enceladus' icy shell behaves as a thin elastic layer, perhaps only a few tens of kilometres thick.

Orbital apocenter is not a sufficient condition for HST/STIS detection of Europa’s water vapor aurora

“…Less pronounced putative aurora anomalies detected in previous HST observations have similarly been speculated to originate from plume activity connected to tidal stress effects (8). Polar surface fractures are principally expected to experience tension during the apocenter phase (17), although tension and compression periods depend on the details of the source regions and vary with longitude, latitude, and fault orientation (18). Tensile stresses on fractures possibly drive the opening of faults and subsequent escape of water from the subsurface (14).…”

Association of the jets of Enceladus with the warmest regions on its south-polar fractures

“…However, tidal-stress calculations 5 , which predict that jet activity should be greatest at times when rifts are in tension, show that the area encompassed by CIRS F would have been under compression during most of our observations. Therefore, if that model is correct, it is plausible that the CIRS pointing is accurate and the region instead periodically produces a jet that we were unlucky enough to miss.…”

Tidal Venuses: Triggering a Climate Catastrophe via Tidal Heating

“…Tidal heating is responsible for the volcanic activity on Io (Peale et al, 1979) and probably the geysers of Enceladus (Hansen et al, 2006;Porco et al, 2006;Hurford et al, 2007). Tidal theory has a long and established body of work; however, tidal processes remain poorly understood.…”