GEOLOGIC AND TOPOGRAPHIC MAPPING OF TOOTING CRATER, MARS

Very young, large (>25 km), morphologically fresh impact craters are rare on Mars, which is unfortunate as they could provide information about the target properties and the impact cratering process. Tooting crater is ~29 km in diameter, is located at 23.4N, 207.5E, and is one such example classified as a multi-layered ejecta crater. We have created digital elevation models (DEMs) for the crater from stereo CTX and HiRISE images. These DEMs have a spatial resolution of ~50 m for CTX data and 2 m for HiRISE data, and are referenced to all of the available individual MOLA data points within the image (~5,000 and 800 respectively). From these DEMs, we can refine our knowledge of the dimensions of Tooting crater; a profile around the rim crest perimeter reveals >600 m of relief (rising to 984 m above the pre-existing datum), the central peak is 1,150 m high, and that the lowest (southern) part of the floor is 1,270 m below the pre-existing datum. We have also studied the rim and interior walls of Tooting crater to document candidate examples of impact melt flows and debris flows in order to constrain the potential flow formation mechanisms. Four flow types have been identified; including possible impact melt sheets and three types of debris flows. Extensive structural failure has modified the northern half of the crater inner wall and we interpret this to have resulted in the destruction of any impact melt emplaced, as well as volatile-rich wall rock. Impact melt flows are fractured on the meter- to decameter scale, have ridged, leveed lobes and flow fronts, and cover an area >6 km x 5 km on the southern rim. Debris flows are found on both the inner wall and rim of the crater, are ~1-2 km in length, and vary from a few tens of meters to >300 m in width. These flows exhibit varying morphologies, from a channelized, leveed flow with arcuate ridges in the channel, to a rubbly flow with a central channel but no obvious levees. Outcrops of gullied and fluted wall material occur between 550 to 800 m above the floor. Water appears to have been released from these outcrops and subsequently fed the identified ridged and lobate flows, and indicates that several layers of the target were wet at the time of impact. The study indicates that water existed within the target rocks at the time of crater formation, and that both melt and fluidized sediment were generated during this event.