Tooting crater: Geology and geomorphology of the archetype large, fresh, impact crater on Mars

The 27.2km diameter Tooting crater is the best preserved young impact crater of its size on Mars. It offers an unprecedented opportunity to study impact-related phenomena as well the geology of the crust in the Amazonis Planitia region of Mars. For example, the nearly pristine condition enables the partial reconstruction of the sequence of events for crater formation, as well as facilitates a comparison to deposits seen at the Ries crater in Germany. High-resolution images taken by the High Resolution Imaging Science Experiment (HiRISE) and Context Camera (CTX) on the Mars Reconnaissance Orbiter spacecraft have revealed a wealth of information on the distribution of features within the crater and beyond the rim: a large central peak, pitted material on the floor and terrace blocks, lobate flows interpreted to be sediment flows, impact melt sheets, four discrete layers of ejecta, and an asymmetric secondary crater field. Topographic data derived from the Mars Orbiter Laser Altimeter (MOLA) and stereo HiRISE and CTX images show that the central peak is ∼1100m high, the lowest point of the crater floor is 1274m below the highest part of the rim, and the crater rim has ∼600m of variability around its perimeter. Layering within the cavity walls indicates ∼260m of structural uplift of the target material, which constitutes ∼35% of the total relief of the rim. Abundant evidence is found for water flowing down the cavity walls, and on the surface of the ejecta layers, both of which took place sometime after the impact event. Thickness measurements of the ejecta layers reveal that the continuous blanket is remarkably thin (∼3–5m) in some places, and that the distal ramparts may be ∼60m high. Crater counts made on the ejecta layers indicate a model age of