The floatability of aerosols and wave damping on Titan’s seas

Abstract

Titan, Saturns 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 Titans 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

Surface Energy of the Titan Aerosol Analog "Tholin"

“…Several groups have measured the densities of tholins produced with different experimental conditions and setups using different density measurement techniques, which varies between 500-1400 kg/m 3 (Imanaka et al, 2012;Hörst & Tolbert, 2013;. The density of the Titan's lakes (a mixture of methane, ethane, and nitrogen) is estimated to be around 450-700 kg/m 3 (Cordier & Carrasco, 2019). If the density of Titan haze particles is smaller than the density of the lake liquids, they would float on Titan's lakes.…”

“…When the haze particles fall towards the polar regions of Titan, they may interact with the liquid hydrocarbon lakes. If the aerosols are able to float and form an organic film on the lake surface, it could reduce the momentum, radiation, matter, and heat transfer between the atmosphere and the seas (Cordier and Carrasco, 2019). For example, the momentum transfer could be reduced due to the aerosol film and could thus dampen the lake surface waves, which could explain Cassini's observations suggesting that waves have very low amplitudes (Stephan et al, 2010;Barnes et al, 2011;Soderblom et al, 2012;Zebker et al, 2014;Grima et al, 2017).…”

Imaging Titan’s Organic Haze at Atomic Scale

“…These molecules are for example good UV absorbers and thus modulate the radiative balance of the atmosphere (Brassé et al 2015). This chemical structure would also influence the surface energy of the haze particles, controlling their wettability with liquid/solid hydrocarbons and nitriles: it would impact their propensity to trigger methane rains in the troposphere and/or to transiently float at the lake surfaces of Titan (Cordier & Carrasco 2019;Yu et al 2020). More generally this work showed the potential of AFM technique to reveal the chemical structure of complex organic material of interest for astrochemistry, opening new perspectives in the chemical analysis of rare and complex material such as organic matter contained in meteorites or in the frame of future sample return missions.…”

Science goals and new mission concepts for future exploration of Titan’s atmosphere, geology and habitability: titan POlar scout/orbitEr and in situ lake lander and DrONe explorer (POSEIDON)

“…However, the exact aerosol content of these lakes as well as the amount that could have sedimented at the bottom of the lakes still remain unconstrained. The presence of a floating film has been already proposed [51], the existence of such a deposit could be easily detected by a Titan lake lander or a drone with the capability to land and float on liquids (hydrodrone). The determination of its nature (monomolecular layer?…”