1. Longitudinal Dunes on Titan as Indicators of Regional and Local Winds J. Radebaugh, R. Lorenz, J. Lunine, S. Wall, G. Boubin, E. Reffet, R. Kirk, R. Lopes, E. Stofan, L. Soderblom, M. Allison, F. Paganelli, and the Cassini RADAR Team

2. Thousands of dunes on Titan Dark to Cassini RADAR, 2.17 cm 2-3 km wide 2-3 km apart tens-100s km long

3. Diverge around regions of high topography Aligned in direction of other wind indicators Thousands of dunes on Titan

4. Longitudinal dune type One dominant wind direction aligned with axis = W-E Lesser off-axis winds Other types (star, barchan) rarely form, in lee of topography

6. Bright/dark from Radar illumination Bright from underlying bedrock

9. Global dune coverage DUNES MAY COVER ~20% OF TITAN’S SURFACE Currently 6% of Titan observed to contain dunes in SAR images Not yet 20% total SAR coverage

10. T13 T3 T8

11. T19 T16 T8T17

12. Dunes binned in 5 degree boxes; vectors = mean azimuth

13. Dunes on Earth also radar-dark, and found at +- 30°

14. The presence of dunes implies sufficient wind, enough sediment, and dry conditions during their formation.

15. Dunes on Earth also radar-dark, and found at +- 30° The presence of dunes implies sufficient wind, enough sediment, and dry conditions during their formation. Recent general circulation models (e.g. Rannou et al., 2006) predict low humidities at low latitudes, and damp conditions near the poles.

16. Dunes on Earth also radar-dark, and found at +- 30° The presence of dunes implies sufficient wind, enough sediment, and dry conditions during their formation. Recent general circulation models (e.g. Rannou et al., 2006) predict low humidities at low latitudes, and damp conditions near the poles. Particles may have been carried from polar regions to equatorial regions to be reworked into dunes