Planet formation and protoplanetary dust

Abstract

Abstract Planet formation is a very complex process through which initially submicron-sized dust grains evolve into rocky, icy, and giant planets. The physical growth is accompanied by chemical, isotopic, and thermal evolution of the disk material, processes important to understanding how the initial conditions determine the properties of the forming planetary systems. Here we review the principal stages of planet formation and briefly introduce key concepts and evidence types available to constrain these. Tiny solid cosmic particles – often referred to as “dust” – are the ultimate source of solids from which rocky planets, planetesimals, moons, and everything on them form. The study of the dust particles' genesis and their evolution from interstellar space through protoplanetary disks into forming planetesimals provides us with a bottom-up picture on planet formation. These studies are essential to understand what determines the bulk composition of rocky planets and, ultimately, to decipher the formation history of the Solar System. Dust in many astrophysical settings is readily observable and recent ground-and space-based observations have transformed our understanding on the physics and chemistry of these tiny particles. Dust, however, also obscures the astronomical view of forming planetary systems, limiting our knowledge. Astronomy, restricted to observe far-away systems, can only probe some disk sections and only on relatively large scales: the behavior of particles must be constrained from the observations of the whole disk. However, planet formation is a uniquely fortunate problem, as our extensive meteorite collections abound with primitive materials left over from the young Solar System, almost as providing a perfect sample-return mission from a protoplanetary disk.