Influence of Dust Grain Evolution on the Structure of Protoplanetary Disks.

he formation and composition of planets is a direct consequence of the processing of solid dust particles in protoplanetary disks: e.g. grain growth, dust settling, crystallization, and segregation of different dust species. Understanding the connections between these effects and how they vary as a function of time is the first step to producing a map of how planet-forming materials are distributed in disks, providing initial conditions for planet formation and evolution models. These will be necessary to analyze the composition and migration history of increasingly large numbers of confirmed exoplanets. Here I present near-, mid-, and far-infrared observations of young protoplanetary disks and their surroundings to identify when grain processing starts and how far it proceeds in the first 1-2Myr, by which time planet formation is observed. Using Spitzer IRS 5-40um spectra, I construct an extinction curve for molecular clouds, which I use to measure dust processing in IRS spectra of the youngest disks (