Total Sand Volume Estimates on Titan from Cassini SAR, HiSAR and ISS

Introduction: Observations of characteristics of sand seas on Saturn's moon, Titan, confirm similarities with Earth's deserts [1]. A careful study of details of these characteristics, such as sand sea areas, sand vol-umes, dune and inselberg morphologies, and sediment sources and transport will help to unveil the evolution-ary history of Titan's surface and climate. Nearly all dunes on Titan are linear in form [1,2] and are concen-trated within the equatorial region [1,2,3,4]. On Titan, dunes are similar in size, radar reflectivity, and mor-phology to those imaged in Earth's Namib, Saharan, and Saudi Arabian deserts [1,2]. This similarity of morphology suggests that there must be, or have been, sufficient wind, sediment supply, and collection area for the dunes to form. Dunes and sand seas on Titan represent the results of major, global atmospheric and surface processes [1,2,3]. Understanding these regions is key to discover-ing the evolutionary history of the surface and atmos-phere of Titan, and to better understanding similar landforms and processes on Earth. This project is focused on inferring the mode and time frame of sand sea sediment accumulation by quantifying the area and estimating the volume of dune fields across Titan. This is the first detailed study of sand sea areas using images from Cassini's Imaging Science Subsystem (ISS) in conjunction with Cassini SAR images. Unlike SAR images, ISS images have 100% coverage of the sand sea latitudes but at lower resolution [5]. Precise calculations of the areas of sand seas, along with dune spacing and heights [6], will allow accurate estimates of total sand volume and will help to further refine the organic inventory from dunes [7,4]. Presented here are the preliminary results from a detailed study of areas of all dunes on Titan from SAR/HiSAR, areas of Titan's Fensal and Aztlan sand seas using Cassini SAR and ISS and an estimate for the total organic inventory from dunes on Titan. Dune Areas from SAR/HiSAR: We identified where dunes are located within SAR and HiSAR im-ages to calculate the areal extent of all dune areas im-aged by Cassini SAR/HiSAR on Titan. Calculating the areas of sand seas is challenging, given the global cov-erage of moderate-resolution (350 m) SAR images of only ~40%. With the added use of slightly poorer-resolution HiSAR images global coverage increases to ~50%. Within SAR-imaged areas, dune sands and non-dune bedrock are clearly distinguished, so our estimate of areal coverage in SAR-imaged areas is probably good [3]. We classified dune material as being SAR dark and linear in morphology and excluded SAR-bright mountains and substrate and other non-dune, SAR-dark features, similar to [4] (Fig. 1a). Each dune field was outlined in ESRI's ArcMap 10