On the origins and composition of planetesimals through studies of circumstellar disks

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A fundamental complication in understanding how planets are assembled and interact with each other and other bodies (like comets and asteroids) has been our inability to directly observe the formation and evolution of these bodies. New facilities are now opening a new window on circumstellar disks, the location where all planets form, providing us with an ability to probe how systems evolve and to test some key assumptions about our own solar system's origins. This research proposal will target key disk systems to utilize the measurements of gases and solids in those disks to inform our understanding of the solar system's earliest times. Within the solar system, measurements of key chemical tracers, such as the ratio of deuterium, a variant of hydrogen with an extra neutron, to hydrogen (D/H) are made toward comets and asteroids to understand how those objects have moved around in the Solar System since their formation. Underpinning this model is the assumption that the D/H ratio in the early solar disk was low near the sun and higher further away. Using recently identified young systems in which comets and asteroid formation has begun or is complete but the gas disk remains, we will measure with the ALMA telescope the D/H ratio for a number of disk systems to verify this aspect of the early Solar System model, thereby enhancing our understanding of how the planets and disk (comets and asteroids) have evolved and interacted with each other. In addition, using other facilities like the Gemini Planet Imager (GPI) and the soon to be launched James Webb Space Telescope, we will measure the motions of gas in the inner regions of disks and compare them to the locations of solids in order to explain how the systems evolve dynamically through collisions and loss of material over time. Using these data, we will place constraints on the migration of large (planets) and small (asteroids and comets) bodies within planetary systems.*My goal with this proposal is to maximize Canada's scientific output of ALMA (the Atacama Large Millimeter/submillimeter Array, the first billion dollar ground based telescope) and GPI disk science. The students funded by this proposal will augment the population of Canadian-based researchers who work in one of the key areas of in which ALMA and GPI are designed to excel: evolution of planetary systems within circumstellar disks.* **