Geologic Structure of the Vera Rubin ridge and clay-bearing Glen Torridon region, Gale Crater, Mars

Mount Sharp is a 5km high mound of lithified sediments in the center of Gale Crater on Mars. The Curiosity rover has been traversing this field site since its arrival in 2012. We study the complex depositional and geologic history of the region by specifically examining the bedding geometries of exposed bedrock along the traverse. Measurements from orbital stereo topographic observations display beds dipping 2-5 degrees away from Mount Sharp. The orbital results allow for a larger scale measurement (100s of meters). In contrast, stereo topographic data from the Curiosity rover allows for a description of bedding geometries on finer scales. We compare in situ measurements to the orbitally-derived data from the Vera Rubin ridge and also implement this characterization method as the rover travels through the Glen Torridon region.

For this analysis, we utilize stereo imaging from the Curiosity rover's Navigation cameras and Mast cameras. We surveyed along the rover traverse from Sol 1800 to the present for suitable outcrops. Our dataset is derived from stereo mosaics of competent bedrock within 10-15 m distance from the rover to allow for precise measurements from the stereo topographic models. Layers are traced on the original images and the [x y z] data are extracted for each pixel. Bedding dip and dip azimuth are calculated by fitting a planar surface to the traced [x y z] points using ordinary linear regression. Regression is performed within a rotated coordinate plane [x' y' z'], where z' is along the camera's optical axis for each image. This is done to minimize residuals in the range direction.

Our resulting dataset is composed of 800 measurements from 24 sites along the Vera Rubin ridge and in the clay-bearing Glen Torridon region. The results from the Vera Rubin ridge show an average dip of 2.4 +/- 0.3 degrees to the northwest, away from the center of Mount Sharp and provide validation for the orbitally-derived measurements at Mount Sharp. The data from the clay-bearing Glen Torridon region exhibit notable variations on the order of 10s of centimeters. We attribute this to small-scale sedimentary structures, depositional trends, and post-depositional deformation. These results, and continued results along the rover traverse are critical in determining the history of sedimentary deposition and modification in Gale crater.