To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2009.06.003 Byline: Sarah J. Morrison, Peter C. Thomas, Matthew S. Tiscareno, Joseph A. Burns, Joseph Veverka Keywords: Saturn; Satellites; Surfaces; Satellites; Shapes; Satellites; Dynamics Abstract: High-resolution images from the Cassini Imaging Science Subsystem (ISS) show parallel sets of grooves on Epimetheus and Pandora. Grooves have previously been observed on other satellites and asteroids, including Phobos, Gaspra, Ida, Eros, and minor occurrences on Phoebe. Sets of parallel grooves are so far observed only on satellites known or likely to be subject to significant tidal stresses, such as forced librations. Grooves on asteroids and on satellites not subject to significant forced librations occur in more globally disorganized patterns that may reflect impacts, varying internal structures, or even thermal stresses. The patterns and individual morphologies of grooves on the tidally-affected satellites suggest fracturing in weak materials due to tidal stresses and forced librations. Author Affiliation: Cornell University, Center for Radiophysics and Space Research, Space Sciences Building, Ithaca, NY 14853, USA Article History: Received 23 April 2009; Revised 1 June 2009; Accepted 3 June 2009