Production and global transport of Titan’s sand particles

Abstract

Previous authors have suggested that Titan's individual sand particles form by either sintering or by lithification and erosion. We suggest two new mechanisms for the production of Titan's organic sand particles that would occur within bodies of liquid: flocculation and evaporitic precipitation. Such production mechanisms would suggest discrete sand sources in dry lakebeds. We search for such sources, but find no convincing candidates with the present Cassini Visual and Infrared Mapping Spectrometer coverage. As a result we propose that Titan's equatorial dunes may represent a single, global sand sea with west-to-east transport providing sources and sinks for sand in each interconnected basin. The sand might then be transported around Xanadu by fast-moving Barchan dune chains and/or fluvial transport in transient riverbeds. A river at the Xanadu/Shangri-La border could explain the sharp edge of the sand sea there, much like the Kuiseb River stops the Namib Sand Sea in southwest Africa on Earth. Future missions could use the composition of Titan's sands to constrain the global hydrocarbon cycle. We chose to follow an unconventional format with respect to our choice of section headings compared to more conventional practice because the multifaceted nature of our work did not naturally lend itself to a logical progression within the precribed system. Lorenz et al. (2006) [1] discovered dunes on Saturn's moon Titan using Cassini RADAR observations. The dunes are overwhelmingly longitudinal in form. On Earth, longitudinal dunes form in bimodal wind regimes where the two modal wind directions differ by more than 90°. The net transport direction for longitudinal dunes on any planet is along the crest, rather than across the crests as for transverse dunes. Radebaugh et al. (2008) [2] deduced that Titan's net sand transport direction is west-to-east. That result derives from analysis of the patterns of dune deflection around