Water is one of the key volatile molecules required for life on Earth. However, it is highly depleted on Earth and may have required delivery from an external volatile reservoir. Recent studies of the far-infrared ice features in protoplanetary disks around low-mass stars have found evidence for volatile-rich planetesimal reservoirs still embedded in primordial gas disks around ~2 Myr old stars, much earlier than expected, but with ice/rock ratios of ~0.5 (less than the solar value). Now, using novel tracers of the bulk atomic abundances of the inner disk, we present evidence for even earlier formation of icy planetesimals, during the Class I protostellar stage. These planetesimals could have larger ice/rock ratios, suggesting that the previous low values may be the result of physical processing. We discuss the implications of this result for survival of complex pre-biotic molecules embedded in the water ice from the molecular cloud stage into these planetesimals.

Does the early planetesimal get the water?

2019 Fall National Meeting

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