Atmospheric/Exospheric Characteristics of Icy Satellites

Abstract

The atmospheres/exospheres of icy satellites greatly vary from one to the next in terms of density, composition, structure or steadiness. Titan is the only icy satellite with a dense atmosphere comparable in many ways to that of the Earth's atmosphere. Titan's atmosphere prevents the surface from direct interaction with the plasma environment, but gives rise to Earth-like exchanges of energy, matter and momentum. The atmospheres of other satellites are tenuous. Enceladus' atmosphere manifests itself in a large water vapor plume emanating from surface cracks near the south pole. Io's SO 2 atmosphere originates from volcanoes. Europa's tenuous O 2 atmosphere is produced by intense radiation bombardment. This chapter reviews the characteristics of the atmospheres of Titan, Enceladus, Io and Europa based on observations. A. Coustenis ( ) LESIA, Observatoire de Paris-Meudon, 5, pl. Jules Janssen,

Geomorphological Analysis of the Southwestern Margin of Xanadu, Titan: Insights on Tectonics

“…Present‐day surface‐atmosphere interactions make aeolian, fluvial, pluvial, and lacustrine processes prominent on a scale seen only on Earth (Lopes et al., 2010, 2020). The satellite's atmosphere consists mainly of nitrogen ( ∼97%), methane ( ∼1.4% in the troposphere, 5% at the surface), and hydrogen (∼0.2%), with traces of more complex hydrocarbons, nitriles, oxygen compounds, and argon as analyzed by the Huygens probe (Coustenis, 2005; Coustenis et al., 2010; Dalton et al., 2010). Under Titan's surface conditions (pressure ∼1.5 bars; temperature ∼91–95 K), methane () and ethane () are both able to condense out of the atmosphere and precipitate to the surface, where the fluid runoff concentrates, incises channels, and transports sediment (Birch et al., 2017; Hayes et al., 2018; Jaumann et al., 2008; Lorenz et al., 2008; Lunine & Lorenz, 2009).…”

Planetary space weather: scientific aspects and future perspectives

“…The ions of the Jovian magnetosphere impacting the moon surfaces release material via direct ion sputtering and radiolysis (Johnson 2001). Considering that water ice is the major surface component, the generated exosphere is expected to be a mixture of H 2 O, O 2 and H 2 and of some other water products, such as OH and O (Shematovich et al 2005;Smyth & Marconi 2006;Coustenis et al 2010;Dalton et al 2010;Plainaki et al 2012). Exospheric H 2 O and H 2 are expected to dominate at higher altitudes, except in a constrained region above the moons'subsolar point where sublimated water can locally have increased densities (Plainaki et al 2012.…”

“…10 See Teolis et al (2010). 11 See Waite et al (2004), Coustenis et al (2010). 12 For Europa see Khurana et al (1998).…”

Organic chemistry in planetary satellites of gas giants and implications for habitability

“…The appropriate spectral range for "HabStars" is presently considered to be "early F" or "G", to "mid-K" temperatures of 4000-7000 K; the Sun, a G2 star, is well within these bounds). The outer solar system is potentially a huge reservoir of water in the form of ice (Coustenis et al 2010, Coustenis & Encrenaz 2013. With the exception of Titan, the icy moons with possible subsurface oceans and/or activity reside in giant planet magnetospheres, but Enceladus and Triton are not in the magnetospheric section with the most extreme surface irradiation harmful to organics.…”