Cometary Isotopic Measurements

Bockelée‐Morvan, Dominique; Calmonte, Ursina; Charnley, Steven B.; Duprat, J.; Engrand, C.; Gicquel, A.; Hässig, Myrtha; Jehin, Emmanuël; Kawakita, Hideyo; Marty, Bernard; Milam, Stefanie N.; Morse, A. D.; Rousselot, P.; Sheridan, S.; Wirström, E. S.

doi:10.1007/978-94-024-1103-4_5

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“…Determination of the abundance ratios of the stable isotopes of the light elements, like D/H ratios, in different objects of the solar system provides important clues to the study of its origin and early history. Astronomical observations of the characteristic atomic and molecular emissions or absorptions from the interstellar space through ground-and/or space-based telescopes become the most important way to gain the isotopic abundance ratios in comets (15,57). However, the D/H ratios returned by these measurements deviate significantly from Earth's water D/H ratio, which brings back to the table the long-standing question whether or not water on Earth was delivered by comet impacts.…”

Section: Potential Relevance To the D/h Isotopic Fractionation In The Solar Systemmentioning

confidence: 99%

Strong isotope effect in the VUV photodissociation of HOD: A possible origin of D/H isotope heterogeneity in the solar nebula

et al. 2021

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The deuterium versus hydrogen (D/H) isotopic ratios are important to understand the source of water on Earth and other terrestrial planets. However, the determinations of D/H ratios suggest a hydrogen isotopic diversity in the planetary objects of the solar system. Photochemistry has been suggested as one source of this isotope heterogeneity. Here, we have revealed the photodissociation features of the water isotopologue (HOD) at λ = 120.8 to 121.7 nm. The results show different quantum state populations of OH and OD fragments from HOD photodissociation, suggesting strong isotope effect. The branching ratios of H + OD and D + OH channels display large isotopic fractionation, with ratios of 0.70 ± 0.10 at 121.08 nm and 0.49 ± 0.10 at 121.6 nm. Because water is abundant in the solar nebula, photodissociation of HOD should be an alternative source of the D/H isotope heterogeneity. This isotope effect must be considered in the photochemical models.

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Section: Potential Relevance To the D/h Isotopic Fractionation In The Solar Systemmentioning

confidence: 99%