Water and Volatiles in the Outer Solar System

Abstract

Space exploration and ground-based observations have provided outstanding evidence of the diversity and the complexity of the outer solar system. This work presents our current understanding of the nature and distribution of water and water-rich materials from the water snow line to the Kuiper Belt. This synthesis is timely, since a thorough exploration of at least one object in each region of the outer solar system has now been achieved. Next steps, starting with the Juno mission now in orbit around Jupiter, will be more focused on understanding the processes at work than on describing the general characteristics of each giant planet systems.

Infrared Observations of Ganymede From the Jovian InfraRed Auroral Mapper on Juno

“…The most prominent spectral feature is the absorption band of water ice centered at 2 µm, which has been discussed in the Introduction and whose band depth varies over Ganymede's surface. To map crystalline versus amorphous water ice based on near‐infrared spectra, one needs to measure three diagnostic spectral indices: the depth of the 1.65‐µm band, the shape and center of the 2.0‐µm band, and the strength and shape of the 3.1‐µm reflectance peak coming from the Fresnel reflection off the facets of the water ice grains on the surface (e.g., Grasset et al., 2017; Mastrapa et al., 2009). Unfortunately, the 1.65‐µm feature is out of the JIRAM range of sensitivity, while only half of the 2.0‐µm band is seen, ruling out the possibility of using these two features.…”

The archaeal class Halobacteria and astrobiology: Knowledge gaps and research opportunities

“…Water is essential for the existence and development of all known life forms, so the search for life in other parts of our solar system and beyond is directly linked with the existence of this vital substance. Luckily for our pursuits, water seems to be more abundant than previously thought (Nimmo and Pappalardo, 2016;Grasset et al, 2017;Greenwood et al, 2018;Schörghofer et al, 2021); there is now evidence that water deposits exist on Mars (Ojha et al, 2014;Martín-Torres et al, 2015;Stillman et al, 2017;Rivera-Valentín et al, 2020;Lauro et al, 2021;Deutsch et al, 2022) as well as on several icy moons (Spencer and Nimmo, 2013;Vance et al, 2014;Hayes, 2016;Jia et al, 2018;Genova et al, 2022). Despite several unknowns, these water bodies outside our planet appear to contain high levels of salt, including perchlorate (Navarro-González et al, 2010;Oren et al, 2014;Martín-Torres et al, 2015;Lauro et al, 2021).…”

Volatile evolution and atmospheres of Trans-Neptunian objects

“…We detail the evidence for the presence of such ices below and summarize it in Table 1. See deBergh et al 2013, Brown 2008, and Grasset et al 2017 for earlier reviews, and the chapter by Barucci and Merlin (2019, this volume) for more general discussion of the composition of TNO surfaces. Despite attempts to characterize surface compositions with photometric systems (Trujillo et al 2011, DalleOre et al 2015, spectral resolution of at least 500 seems to be needed for definitive detections of volatile ices, and we focus on spectral data below.…”