DUNES ON SATURN'S MOON TITAN FROM CASSINI: MORPHOLOGY, COMPOSITION AND INDICATORS OF WIND AND CLIMATE

Dunes on Saturn’s largest satellite Titan are a dominant landform comprising at least 15% of the surface, and they represent the end product of many familiar physical processes acting in alien conditions. Winds currently blow in Titan’s atmosphere, which is like Earth in composition (nitrogen-rich) and surface pressure. The winds transport particles of complex organic composition, possibly eroded into sand sizes by methane rainfall, wind erosion or spallation, or the particles collect and settle directly from the atmosphere. These sands then accumulate into large, planet-encircling sand seas concentrated near the equator. Dunes on Titan are predominantly linear and similar in size and form to the large dunes of the Namib, Arabian and Saharan sand seas. They likely formed from wide bimodal winds and appear to undergo net sand transport to the east. Their singular form across the satellite indicates Titan’s dunes may be highly mature, and may

reside in a condition of stability that permitted their growth and evolution over long time scales. The dunes are among the stratigraphically youngest surface features, as even river channels do not widely affect their morphologies. However, reorganization time scales of large linear dunes on Titan are likely tens of thousands of years. Thus, Titans' dune forms may be long-lived and yet be actively undergoing sand transport. This work addresses current research on dunes on Titan during the Solstice Mission (to end in 2017). It discusses results of Cassini data analysis and modeling of conditions on Titan, focusing on global dune distribution, dune maturity and pattern analysis, and potential stabilized forms and implications for climate change. In addition, it draws comparisons with observations and models of linear dune formation and evolution on Earth.