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

Abstract

Titan, the enigmatic large moon of Saturn, is unique because it is the only satellite of the solar system that is surrounded by a dense atmosphere. Thick layers of photochemical organic aerosols shroud the surface and sediment to the ground. In polar regions, large lakes and seas of liquid hydrocarbons were discovered by the Cassini–Huygens mission. Aerosols that sediment above the lakes run into a liquid surface in which new interactions can take place. In this paper, we address the question of the first contact between the aerosols and the lakes: do the aerosol particles float or rapidly sink into the lakes? We investigated the possible effects of a floating film or slick formed by this organic material and other products of the atmosphere. We also compared the wave damping effect on Earth's oceans to the Titan counterparts. According to this work, Titan appears to be a much more favourable place for such a damping. By inhibiting the formation of the first ripples, this phenomenon could impede the existence of waves at wavelengths larger than a few centimetres. This effect could explain the remarkable smoothness of the sea surface often noticed in Cassini observations.

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Fig. 1: A monomer (symbolized by a shaded disk) in contact with a liquid, which is represented in blue.
Fig. 2: Comparison of the wave damping efficiency due to a floating film in the Titan context and under Earth conditions.
Fig. 3: The relative damping ratio y as a function of the wavelength λ in the case of a thin finite thickness film deposited at the surface of water, that is, in the context of Earth.

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Code availability

The codes used to generate the plots in this paper are available from the corresponding author upon reasonable request.

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Acknowledgements

N.C. thanks the European Research Council for funding via the ERC PrimChem project (grant agreement no. 636829). This work was also supported by the Programme National de Planétologie (PNP) of CNRS-INSU co-funded by CNES. The authors thank S. Lebonnois, J. Vatant d’Ollone, T. Tokano and B. Charnay for fruitful scientific discussions.

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D.C. wrote the paper and performed numerical simulations. N.C. provided expertise concerning the properties of Titan’s aerosols.

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Correspondence to Daniel Cordier.

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Cordier, D., Carrasco, N. The floatability of aerosols and wave damping on Titan’s seas. Nat. Geosci. 12, 315–320 (2019). https://doi.org/10.1038/s41561-019-0344-4

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