List of contributors; 1. Planetesimals Benjamin P. Weiss; Part I. Dynamical Evolution: 2. Signatures of hit and run collisions Erik Asphaug; 3. Using the main asteroid belt to constrain planetesimal and planet formation William Bottke and A. Morbidelli; Part II. Chemical and Mineralogical Diversity: 4. Differentiation under highly reducing conditions: new insights from meteorites and mercury Timothy J. McCoy and Emma S. Bullock; 5. Origin and evolution of volatile-rich asteroids Julie Castillo-Rogez and Edward Young; 6. Silicate melting and volatile loss during differentiation in planetesimals Roger R. Fu, Edward Young, Richard C. Greenwood and Linda T. Elkins-Tanton; 7. Iron and stony-iron meteorites: evidence for the formation, crystallization, and early impact histories of differentiated planetesimals Alex M. Ruzicka, Henning Haack, Nancy L. Chabot and Edward R. D. Scott; 8. Arguments for the non-existence of magma oceans in asteroids Lionel Wilson and Klaus Keil; 9. Magnetic fields on asteroids and planetesimals Aaron Scheinberg, Roger R. Fu, Linda T. Elkins-Tanton, Benjamin P. Weiss and Sabine Stanley; 10. Magnetic mineralogy of meteoritic metal: paleomagnetic evidence for dynamo activity on differentiated planetesimals Richard J. Harrison, James F. J. Bryson, Claire I. O. Nichols and Benjamin P. Weiss; 11. Chronology of planetesimal differentiation Thorsten Kleine and Meenakshi Wadhwa; 12. Stable isotope evidence for the differentiation and evolution of planetesimals Anat Shahar, Paul Savage and Fred Moynier; Part III. Asteroids as Records of Formation and Differentiation: 13. Composition of Solar System small bodies Pierre Vernazza and Pierre Beck; 14. Evidence for differentiation among asteroid families Thomas H. Burbine, Francesca E. DeMeo, Andrew S. Rivkin and Vishnu Reddy; 15. Dawn at Vesta: paradigms and paradoxes Carol A. Raymond, Christopher T. Russell and Harry Y. McSween, Jr; 16. Planetesimals in debris disks Andrew N. Youdin and George H. Rieke; Part IV. Early Differentiation and Consequences for Planet Formation: 17. Consequences for planet formation Linda T. Elkins-Tanton; Index.