How asteroids and comets help us decipher how our Solar System formed.

Title: How asteroids and comets help us decipher how our Solar System formed.

Abstract: How did our Solar System form and evolve? What properties did the protoplanetary disk of the Solar System have? Did any of the first solid bodies in the Solar System survive to this day? These questions lie at the heart of planetary science. I will review how the first solid bodies, the so-called planetesimals, formed. The descendants of these bodies are known today as asteroids and comets. These small solar system bodies are paving the way for our understanding of how the Solar System formed and evolved. Almost twenty years ago, the discovery of the giant planet instability explained how the current dynamical structure of the Solar System arose from a much more compact system. Today, we stand at the cusp of another giant leap. Meteorite samples give us constraints on the period before the giant planet instability, the epoch of the protoplanetary disk. But they pose many puzzles. I will explain these puzzling observations and how we are using them to inform our understanding of the formation and evolution of our protoplanetary disk. In particular, I will argue that our protoplanetary disk underwent an initial rapid, almost inflationary, expansion stage. Finally, spacecraft missions like Rosetta, Lucy, and Comet Interceptor have and will provide us with additional high-resolution data on the most pristine small bodies. But to use those spacecraft measurements, we need to understand the formation of planetesimals and their dynamical, thermal, and collisional evolution.