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STScI Astrobiology Lecture Series

Unearthing the Astrochemical Heritage of Solar System Ices

Presented by:  Ilse Cleeves (Harvard-Smithsonian Center for Astrophysics)
Category: Science Colloquia   Duration: 1 hour and 30 minutes   Broadcast date: February 05, 2016
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Tracing the chemical history of water during the formation of solar-type stars sheds light on both the origins of water in our own solar system and, more generally, the availability of water to all nascent planetary systems. One important clue comes from measured enrichments in deuterium relative to hydrogen (D/H) in various solar system water reservoirs relative to that of the bulk nebular gas. Specifically, large D/H enhancements are a product of water formation in very cold environments, facilitated by the presence of high energy particles and photons. These requirements point to two possible origins for solar system water: in situ chemistry in the outer regions of a protoplanetary disk or inheritance from the parent molecular cloud. Using a comprehensive treatment of high energy processes in protoplanetary disks, we find that ion-driven deuterium fractionation in disks is inefficient, especially in the midplane. This lack of cold water formation in the disk implies that the solar system likely inherited a large fraction of its water, and perhaps other primordial ices, from the parent molecular cloud. If the solar system's formation was typical, water should be a common ingredient during the planet formation process.