Surface Energy Of The Titan Aerosol Analog "Tholin"

©NASA

Titan

The photochemical haze produced in the upper atmosphere of Titan plays a key role in various atmospheric and surface processes on Titan.

The surface energy, one important physical properties of the haze, is crucial for understanding the growth of the haze particles and can be used to predict their wetting behavior with solid and liquid species on Titan. We produced Titan analog haze materials, so-called "tholin", with different energy sources and measured their surface energies through contact angle and direct force measurements. From the contact angle measurement, we found that the tholins produced by cold plasma and UV irradiation have total surface energy around 60-70 mJ/m2. The direct force measurement yields a total surface energy of ~66 mJ/m2 for plasma tholin.

The surface energy of tholin is relatively high compared to common polymers, indicating its high cohesiveness. Therefore, the Titan haze particles would likely coagulate easily to form bigger particles, while the haze-derived surface sand particles would need higher wind speed to be mobilized because of the high interparticle cohesion. The high surface energy of tholins also makes them easily wettable by Titan's atmospheric hydrocarbon condensates and surface liquids. Thus, the hazes particles are likely good cloud condensation nuclei (CCN) for hydrocarbon clouds (methane and ethane) to nucleate and grow. And if the hazes particles are denser compared to the lake liquids, they would likely sink into the lakes instead of forming a floating film to dampen the lake surface waves.

Xinting Yu, Sarah Horst, Chao He, Patricia McGuiggan, Kai Kristiansen, Xi Zhang
Comments: 27 pages, 6 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Cite as: arXiv:2010.13885 [astro-ph.EP] (or arXiv:2010.13885v1 [astro-ph.EP] for this version)
Submission history
From: Xinting Yu
[v1] Mon, 26 Oct 2020 20:21:11 UTC (4,742 KB)
https://arxiv.org/abs/2010.13885
Astrobiology, Astrochemistry,

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