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The ancient heritage of water ice in the solar system

Science  26 Sep 2014:
Vol. 345, Issue 6204, pp. 1590-1593
DOI: 10.1126/science.1258055

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Nature or nurture for solar system ices?

We know that life's favorite molecule, water, exists throughout the solar system. What we don't know is whether present water levels reflect the chemical conditions of our parent nebula or whether they result from later reprocessing in the young system. The levels of deuterium and hydrogen in solar system water ice offer a tracer for chemical history, and Cleeves et al. model the processes at play. The analysis suggests that all nascent planetary systems may have the same water resources that we did.

Science, this issue p. 1590

Abstract

Identifying the source of Earth’s water is central to understanding the origins of life-fostering environments and to assessing the prevalence of such environments in space. Water throughout the solar system exhibits deuterium-to-hydrogen enrichments, a fossil relic of low-temperature, ion-derived chemistry within either (i) the parent molecular cloud or (ii) the solar nebula protoplanetary disk. Using a comprehensive treatment of disk ionization, we find that ion-driven deuterium pathways are inefficient, which curtails the disk’s deuterated water formation and its viability as the sole source for the solar system’s water. This finding implies that, if the solar system’s formation was typical, abundant interstellar ices are available to all nascent planetary systems.

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