DUNE AREAS AND SAND VOLUMES ON SATURN’S MOON TITAN FROM CASSINI SAR AND ISS

Observations of sand seas on Saturn’s moon, Titan, reveal similar radar reflectivity and morphologies to those on Earth. Careful study of these and other characteristics, including sand sea areas and volumes, will help to unveil the evolutionary history of Titan’s surface and help researchers to better understand the atmospheric production of organics sourcing these sand seas.

The mode and time frame of sand sea accumulation on Titan are tied to the area and volume of dune fields on the satellite. We calculated this first using only limited coverage Cassini Synthetic Aperture Radar (SAR) data where dunes, visible as linear features, are identifiable. Second, images from Cassini’s Imaging Science Subsystem (ISS) are used in conjunction with Cassini Synthetic Aperture Radar (SAR) images to map dune extents. Unlike SAR images, ISS images have 100% surface coverage but at lower resolution. There is a reasonably clear correlation between dune regions in SAR and regions dark to ISS at 938 nm.

Measurements from SAR data alone, extrapolated globally based on percent coverage, yield results similar to previous studies, ~14% global dune coverage or 12 million km², roughly four times the area of Africa’s Libyan/Egyptian Great Sand Sea. Combined SAR/ISS measurements are completed thus far in the Fensal/Aztlan sand seas; total dune coverage measured for Fensal/Aztlan is 2.3 million km². Percent coverage here suggests a global sand volume of 150,000-300,000 km³. Volume is estimated assuming average dune height h=100 m, average interdune width equal to dune width, and dune shape is prismatic. This equation, V=Ah/4, is used to calculated volume, where A=area.

We will continue mapping in Belet, Shangri-La, and Senkyo Sand Seas based on our SAR/ISS method. Our estimates will be refined as we adjust our assumptions for calculating volume; for example, by incorporating variations in interdune width, dune spacing and sand coverage across Titan.