POLYGONAL IMPACT CRATERS ON IAPETUS
We are applying a technique to identify and analyze PICs on Iapetus using a series of statistical tests. We first test for uniform azimuth distributions for each crater. A set of multi-line segment azimuths and lengths is utilized to test for a uniform distribution of crater rim azimuths. A subsequent test is applied to exclude degraded craters that may be falsely classified as PICs due to non-uniform rim azimuth distributions. The prominent rim azimuth(s) is then determined for identified PICs.
Our preliminary results indicate that PICs are present on Iapetus. In some locations, PICs are proximal to visible linear features and exhibit straight rim segments that parallel these features, supporting the interpretation that they are extensional tectonic fractures with a shared background stress pattern. PICs are also present in regions with no visible tectonic features, indicating that a stress pattern exists although it was not preserved by any visible tectonic features in that area. We are using the 2D numerical program SatStressGUI to model global stresses across the surface of Iapetus to compare the patterns with mapped PIC straight rim segments and visible fractures. Stress and associated modeled fracture maps will be analyzed to investigate the possible global stress mechanisms.