Year: 2025
Type: dissertation
Abstract: Saturn's largest moon, Titan, has a dense reducing atmosphere, where organic aerosols are formed from methane (CH4) and nitrogen (N2) via photochemical reactions.These organic aerosols would deposit on the surface, where an active CH4-based hydrological cycle exists.Thick organic sediments exist as dunes only at low latitude regions of Titan, but not in the middle latitude regions, although both low and middle latitude regions are generally arid.Given that no thick organic sediments exist on middle latitude regions where potentially H2O ice crust exposed, organic aerosols at middle latitudes may have been transported spontaneously.Previous studies, however, have considered that saltation of organic aerosols would occur only by strong winds due to CH4 storms at low latitudes but would not occur by seasonal wind at low and middle latitudes based on the high cohesiveness of Titan's organic aerosol analogs (Titan tholin) measured at room temperature.However, the cohesive force would be different at Titan's surface temperature (~93 K).In addition, various chemical process on the surface of Titan would result in the formation of organic materials with different chemical structures, which would show different cohesiveness.However, the temperature dependence and chemical structure dependence of cohesiveness, which depends on the surface energy and elasticity, of Titan's organic analog materials have been poorly understood.The objectives of the present study are to investigate the temperature and chemical structure dependence of both surface energy (cohesion force) and elasticity (elastic wave velocities) of organic analog materials on Titan.I would also like to express my sincere appreciation to Prof. H. Genda, the chairperson of this thesis, for his kind support and valuable advice throughout my doctoral course.His guidance
Author: Eito Hirai
Institution: Institute of Science Tokyo
Language: English
Topic: Astro and Planetary Science
Subfield: Space and Planetary Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7212465315