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Delivery of Volatiles & Organics: From Earth to Exoearths in the Era of JWST

The Chemical History of Volatiles in Protoplanetary Disks

Presented by: Ruud Visser (Leiden Observatory)
Category: Science Workshops   Duration: 1 hour and 25 minutes   Broadcast date: September 15, 2010
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In order to probe possible pathways for delivering volatiles to the Earth and other rocky planets or exoplanets, it is necessary to understand when and where these volatiles were formed in the first place. We present a model that follows the chemical evolution all the way from pre-stellar cores to protoplanetary disks. It traces gas and dust falling in from the natal cloud core to the star and the disk, and it solves for the abundances of a few hundred gas-phase and grain-surface species as function of time and position. The necessary observational constraints come from data taken with, e.g., the SMA (the PROSAC survey) and Herschel (the WISH and DIGIT key programs). The model predicts that many volatiles are formed already in the infalling envelope, before reaching the disk. They undergo further processing within the disk, thus determining the abundances of complex organic molecules in the building blocks for planets and comets. The predicted abundances of several key species match the abundances observed in comets, but for other species the match is very poor. We discuss what both the good and the poor matches mean for the possible delivery mechanisms for volatiles on Earth and elsewhere.