[M-IS19] Aqua planetology

[MIS19-05] Adhesion force of organic aerosols on Titan

*Eito Hirai^1,2, Yuuki Yasui³, Yasuhito Sekine^2,4,5, Yoshiaki Sugimoto³ (1.Department of Earth and Planetary Sciences, School of Science, Tokyo Institute of Technology, 2.Earth-Life Science Insitute, Tokyo Institute of Technology, 3.Department of Advanced Materials Science, Graduate School of Frontier Sciences, The University of Tokyo, 4.Institute of Nature and Environmental Technology, Kanazawa University, 5.Department of Geophysics, Graduate School of Science, Tohoku University)

Keywords:Titan, Organic aerosols, Adhesion force, Surface energy

Titan’s organic aerosols play many roles in determining the atmospheric structure and in generating surface landforms. Previous work reported adhesion force of laboratory analogs of Titan’s aerosols, called Titan tholin, at room temperature (Yu et al., 2017). However, organic aerosols deposited on Titan’s surface would be chemically altered with liquid methane (Hirai et al., 2023). To our best knowledge, there is no previous study that investigated adhesion force of chemically-altered Titan tholin. In addition, given the low temperatures (70–180 K) of the lower atmosphere and surface of Titan (Fulchignoni et al., 2005), a temperature dependence of adhesion force is an important factor in both the collisional growth and saltation of aerosol particles.
Here, we investigate adhesion forces of both non-altered and chemically-altered Titan tholin at 78 K and 300 K. Titan tholin is produced with a cold plasma irradiation onto a gas mixture of N₂/CH₄ = 90/10 at pressure of ~200 Pa. Chemically-altered Titan tholin is generated by immersing Titan tholin into liquid methane at ~93 K and then dried using a cryochamber. Adhesion forces of Titan tholin are obtained from force-distance curves measured using an atomic force microscope (AFM). Chemically-altered Titan tholin contains more N-bearing polyaromatic compounds than non-altered Titan tholin (Hirai et al., 2023). Higher abundances of aromatic compounds in chemically-altered Titan tholin may result in larger adhesion force than those of non-altered Titan tholin. We will report our experimental results of adhesion forces of non-altered and chemically-altered Titan tholin and discuss roles of chemically-altered organic aerosols in landform formation on Titan.