Exploring the pristine conditions for transforming interstellar dust into planetesimals

The formation and properties of exoplanetary systems is a fascinating question, which has been at the heart of our quest to define mankind and the conditions for life to develop in a broader context.Recent astronomical observations have deeply modified our paradigm of planet formation, as they suggest the so-called ""proto-planetary” disks surrounding T-Tauri stars may actually already host planets. Moreover, we have obtained some of the first observational clues that the dust particles contained in the pristine disk-forming reservoirs that are the embedded protostars may already have significantly evolved from the submicronic dust populating the interstellar medium. These results suggest that dust evolves significantlyalready during the first 0.5 Myrs of the star formation process, and highlight the prime importance of understanding the properties and evolution of dust in young protostars.The PEBBLES project aims at developing a thorough methodology to characterize the properties of dust in embedded protostars, where we know the star and its disk are forming concomitantly. Using an innovative methodology combining cutting edge observational datasets, dust models and numerical models, we aim to transform our understanding of:1) The nature of the dust incorporated in the youngest disks, a key for models of disk evolution towards planetary systems2) The processes at work for dust evolution in young protostars, from envelopes to disk scales3) The efficiency of magnetic fields to couple to the star/disk forming material, and set the disk propertiesBy shedding light on early dust evolution, we will not only address one of the oldest and most challenging question regarding the initial conditions for planet formation in disks around solar-type stars, but also provide new insight to the conditions reigning and their impact on physical processes during the main accretion stage, during which stars acquire most of their properties.""