Asteroid Interiors and Morphology

The past decade has seen an astonishing array of advances across a wide spectrum of important inputs to the problem and mystery of asteroid interiors. These include the development of a large database concerning asteroid component strengths, as evidenced by meteors and meteorites (section 2); the compilation of extensive densities and inferred porosities for asteroids based on groundbased observations (section 3); the development of new computational techniques for the simulation of how asteroid rubble piles deform and fission or shed mass when subject to extreme rotation rates (section 4); and the development of crucial insights into the unique geophysics of specific asteroidal bodies (section 6). This chapter will review these different areas of advancements in an attempt to unify these disparate topics and show where future progress can be made in this field. Knowledge about asteroid interiors is a crucial aspect for understanding these bodies, as it provides clues about their evolutionary history, in turn providing strong constraints on the history of the solar system. Unlike asteroid surfaces, it is impossible to peer directly within or easily take a sample measurement from within a body. Thus the study of asteroid interiors must rely on a combination of measurement and theory to develop constraints on the interior environment. Given these restrictions, previous investigations have studied observable characteristics that may be related to the nature of their interiors. This being said, there are measurement techniques that can probe the interior properties of bodies, in particular through seismic and radar sounding measurements. These are discussed in section 5 and represent a potential source for future advancements in this field. The most accessible features of an asteroid that are related to their interior structure are the mass, density, shape, and spin. These are strongly constrained by the interior structure, and by the strength and mechanical properties of that structure. By focusing on these specific observables, we can start to answer basic questions about these bodies: How strong are they? What is the nature of that strength? Are the interiors rubble piles full of voids at various size scales, or are they solid coherent structures? How do these properties depend on composition, shape, spin, size, or location? Important steps in answering the above questions have occurred since the publication of the Asteroids III volume