THE LINEAR DUNES AND SAND SEAS OF TITAN

The equatorial regions of Saturn’s moon Titan are home to tens of thousands of some of the largest eolian landforms in the solar system – linear megadunes. They are ~1 km wide, spaced 2-4 km, ~100 m high and tens to hundreds of km long. They are highly parallel, with distinct interdune boundaries, along much of their lengths. The interdune regions are in many places free of sand, indicating that dune forming processes are active enough to prevent mass wasting that would erode the dunes. Their sizes and shapes indicate they have been in their conditions of wind strength and direction and sand supply for long time periods, in other words, that they are equilibrium landforms. Exceptions to this exist where defects and superposition relationships can be seen, often near obstacles or at dune field boundaries. Dunes can thus be used to determine sand transport directions and causative wind regimes that extend from the present back through enough time required to assemble or reorganize the large forms. On Earth this can be tens to hundreds of thousands of years. Sand transport on Titan, and time-integrated winds, are generally west to east across Titan’s equatorial regions. Titan’s dunes are organized into sand seas that exist in wide, generally uninterrupted spaces, similar to those on Earth’s large, cratonic deserts. We are investigating the transport and accumulation of sand within and between sand seas through analysis of margin morphologies, variations in dune parameters, and elevation controls. Targeted measurements of dune width, spacing and length are underway for the Belet Sand Sea of Titan, with similar measurements being done in Earth’s Namib Sand Sea for comparison. Broadly, dune width and spacing vary with latitude, likely a result of climatic effects on sediment transport, though variations with elevation and with location relative to upwind margins and intrasandsea obstacles are starting to emerge. Dunes and sand seas observed today on Titan are a result of modern climate, perhaps integrated with climatic conditions in the recent past, just as on Earth. Unraveling the contributions from all the different inputs to produce the visible landforms is the aim of several Titan dune studies.