Surface Energy of the Titan Aerosol Analog "Tholin"

Abstract

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.

arXiv comment27 pages, 6 figures

References in corpus (16)

• Titan's Atmosphere and Climate
• Formation of Silicate and Titanium Clouds on Hot Jupiters
• Microphysics of KCl and ZnS Clouds on GJ 1214b
• Photochemical Haze Formation in the Atmospheres of super-Earths and mini-Neptunes
• Carbon Monoxide Affecting Planetary Atmospheric Chemistry
• In Situ Measurements of the Size and Density of Titan Aerosol Analogues
• Laboratory Investigations of Titan Haze Formation: In Situ Measurement of Gas and Particle Composition
• Bubble streams in Titan's seas as product of liquid N2-CH4-C2H6 cryogenic mixture
• Where does Titan Sand Come From: Insight from Mechanical Properties of Titan Sand Candidates
• Direct Measurement of Interparticle Forces of Titan Aerosol Analogs ("Tholin") Using Atomic Force Microscopy
• Nitrogen-containing Anions and Tholin Growth in Titan's Ionosphere: Implications for Cassini CAPS-ELS Observations
• The floatability of aerosols and waves damping on Titan's seas
• Positive Ion Chemistry in an N${}_2$-CH${}_4$ Plasma Discharge: Key Precursors to the Growth of Titan Tholins
• The Effect of Adsorbed Liquid and Material Density on Saltation Threshold: Insight from Laboratory and Wind Tunnel Experiments
• Bubbles in Titan's seas: nucleation, growth and RADAR signature
• Single particle triboelectrification of Titan sand analogs

Cited by in corpus (8)

• The Composition and Chemistry of Titan's Atmosphere
• Haze Evolution in Temperate Exoplanet Atmospheres Through Surface Energy Measurements
• Haze Formation on Triton
• Material Properties of Organic Liquids, Ices, and Hazes on Titan
• The Fate of Simple Organics on Titan's Surface: A Theoretical Perspective
• Open Questions and Future Directions in Titan Science
• The atmosphere of K2-18 b: The role of hazes, clouds and photoelectrons
• Grain Growth in Escaping Atmospheres: Implications for the Radius Inflation of Super-Puffs