Morrison, S. J. , Thomas, P. C., Veverka, J., Burns, J. A., Tiscareno, M. S., Porco, C. C. (2008). "Grooves on Small Saturnian Satellites: Possible Evidence for Tidal Stressing" American Astronomical Society, DPS meeting #40, #45.04.


Abstract
High-resolution images taken in December 2007 by Cassini's Imaging Science Subsystem (ISS) reveal parallel sets of grooves in the southern hemisphere of Epimetheus. Earlier images had shown grooves in the northern portion of Pandora. On both satellites, these grooves are typically ~600 m across, less than 200 m deep, and less than 10 km in length. These features are interpreted as regolith expressions of fractures or faults in the consolidated portion of the satellites. The major group of grooves on Epimetheus suggests expression of planes perpendicular to the Saturn direction, similar to the pattern of one of the prominent groove sets on Phobos. Pandora's grooves suggest a pattern of planes rotated slightly off the perpendicular to the Saturn direction. Other small Saturn satellites with good image coverage -- Telesto, Hyperion, and Phoebe --do not have such organized patterns of grooves. Grooves on asteroids (Eros, Gaspra, Ida) are likely associated with multiple cratering events and are distinct in pattern from Epimetheus' and Phobos' grooves. Repetitive tidal stressing may explain the differences between satellite and asteroidal grooves. Owing to orbital eccentricities and any non-synchronous spins or librations, tidal stresses vary. For the current orbits of Epimetheus and Pandora, the former produces stress variations that are very modest (103 dyne/cm2) while those due to the latter are larger, perhaps 105 dyne/cm2. If these are to account for the observed grooves, the small moons must be very fragile, perhaps not surprising in view of their high porosities.