Asteroid Interiors

Asteroids represent a geophysical frontier of considerable scientific importance, for these building blocks of planets preserve a compositional and mechanical record of the solar system's origin. They also pose a formidable hazard to life on Earth, while offering potentially enormous resources to benefit solar system exploration. This chapter introduces their geologic subtlety through the theme of strength vs. gravity: Asteroids stand apart from rocks and planets because these primary forces (strength short-range and gravity long-range) achieve an intricate mechanical balance that is only partly understood. Recent findings have turned Earth-based intuition on its head. For example, structurally weak asteroids and comets may, through stress dissipation, be the most highly resistant to catastrophic disruption. Perhaps more surprising, the collisional evolution of bodies the size of a city block may be determined by their minuscule self-gravity. While the fundamental geophysical behavior of asteroids continues to elude us, one idea resonates: Instead of competing for dominance, strength and gravity collaborate over a wide spectrum of sizes and shapes to produce some of the richest structures in nature.