Publication: New look at the origin and the growth mechanism of Titan dunes

Titan, the largest satellite of Saturn, has a thick atmosphere dominated by nitrogen and carbon compounds. This satellite has many similarities with Earth, including a very active weather cucle, essentially controlled by methane, and many landscapes with extremely familar faces in particular huge fields of linea dunes around the equator. Such dune are observed in many terrestrial deserts and even on Mars and are witnesses of the wind regimes and sedimentary environment that shaped them.

These dune fields occupy 17% of Titan’s surface and carry with them valuable information about the climate of the satellite. By combining observations with data from the Cassini spacecraft, orbiting Saturn since July 2004, climate modeling and sediment transport theory, a study conducted by researchers at the Space Campus of the University Paris Diderot, offers a fresh look at mechanisms of growth and propagation of these giant dunes. In particular, it is shown that contrary to what was commonly believed, the dunes are not formed on a bed of mobilized sediment, but elongate by feeding from their own sediment in the direction of the prevailing wind also named resultant drift direction. Thus, the study shows that only powerful gusts from extreme weather events on the equinoxes, actually observed by Cassini during the spring equinox, help explain the orientation and direction of propagation of these dunes. Finally, the researchers added that the meridional sediment transport converges with the equator, satellite areas with the driest weather, thus explaining the segregation of the dunes in the tropical region.

Dunes composed of complex organic species that stretch under the action of wind gusts on the equinoxes (Figure A. Lucas).



A. Lucas, S. Rodriguez, C. Narteau, B. Charnay, T. Tokano, A. Garcia, M. Thiriet, S. Courrech du Pont, A. Hayes, R. Lorenz, O. Aharonson, Growth mechanisms and dune orientation on Titan, Geophys. Research Letters, doi: 10.1002/2014GL060971, 2014.