The floatability of aerosols and waves damping on Titan's seas

Abstract: Titan, Saturn's largest moon, has a dense atmosphere, together with lakes and seas of liquid hydrocarbons. These liquid bodies, which are in polar regions and up to several hundred kilometres in diameter, generally have smooth surfaces despite evidence of near-surface winds. Photochemically generated organic aerosols form a haze that can settle and potentially interact with the liquid surface. Here we investigate the floatability of these aerosols on Titan's seas and their potential to dampen waves. We find that the majority of aerosols are denser than the liquid hydrocarbons, but that some could have liquid-repelling properties. From calculation of the capillary forces, we propose that these 'liquidophobic' aerosols could float and form a persistent film on Titan's seas. We numerically model the wave damping efficiency of such a film under the conditions on Titan, demonstrating that even a film one molecule thick may inhibit formation of waves larger than a few centimetres in wavelength. We conclude that the presence of a floating film of aerosols deposited on Titan's lakes and seas could explain the remarkable smoothness of their surfaces.