Origin and Evolution of Volatile-rich Asteroids

Volatile-rich asteroids represent the largest population, about 42% (DeMeo and Carry, 2014), of objects found between 2 and 3.5 AU. They encompass asteroids from the C complex that are believed to host the parents of most carbonaceous chondrites based on spectroscopic analogies (Hiroi, 1996; Takir et al., 2015), as well as the large icy asteroids found in the outer main belt. The Pand D-type asteroids also found in that region are believed to contain a significant fraction of ices based on their presumed origin from the Kuiper belt (Levison et al., 2009), although no water signatures (ice, hydroxyl, or hydration features) have been detected for these objects. The lack of observational constraints on the physical and chemical properties of these objects makes it difficult to speculate on their internal evolution and they will not be considered further in this chapter. Key science questions surround C-type asteroids. Arguably the most important is whether they are the remnants of a single reservoir of material that formed near their current positions in the main belt and in the neighborhood of the nearby dry asteroids, or if instead they come from multiple, perhaps more distal, reservoirs. Located at the interface between the inner and outer solar systems, the main belt has witnessed the various large-scale planet migration events that may well have shaped the architecture of the solar system (e.g. Levison et al. 2009; Walsh et al., 2012). A likely contribution of volatile material from the outer solar system could affect the long-term chemical and physical evolution of the large asteroids. By analogy with icy satellites, differentiation involving the melting of liquid water carries important implications for the chemical evolution of these objects and their potential contribution to the production of complex organics. The large representatives (>100 km) are believed to have hosted hydrothermal environments for a few million years, offering a playground for prebiotic chemistry (Abramov and Mojzsis, 2011). This idea has also been suggested for Ceres in which liquid media