^1,2,6Lydia J. Hallis, ^1,2Gary R. Huss, ²Kazuhide Nagashima, ^1,2G. Jeffrey Taylor, ³Sæmundur A. Halldórsson, ³David R. Hilton, ⁴Michael J. Mottl, ^1,5Karen J. Meech
¹NASA Astrobiology Institute, Institute for Astronomy, University of Hawai’i, 2680 Woodlawn Drive, Honolulu, HI 96822-1839, USA.
²Hawai’i Institute of Geophysics and Planetology, Pacific Ocean Science and Technology (POST) Building, University of Hawai’i, 1680 East-West Road, Honolulu, HI 96822, USA.
³Scripps Institution of Oceanography, University California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0244, USA.
⁴Department of Oceanography, University of Hawai’i, Marine Sciences Building 304, 1000 Pope Road, Honolulu, HI 96822, USA.
⁵Institute for Astronomy, University of Hawai’i, 2680 Woodlawn Drive, Honolulu, HI 96822, USA.
⁶School of Geographical and Earth Sciences, University of Glasgow, Gregory Building, Lillybank Gardens, Glasgow G12 8QQ, UK.

The hydrogen-isotope [deuterium/hydrogen (D/H)] ratio of Earth can be used to constrain the origin of its water. However, the most accessible reservoir, Earth’s oceans, may no longer represent the original (primordial) D/H ratio, owing to changes caused by water cycling between the surface and the interior. Thus, a reservoir completely isolated from surface processes is required to define Earth’s original D/H signature. Here we present data for Baffin Island and Icelandic lavas, which suggest that the deep mantle has a low D/H ratio (δD more negative than –218 per mil). Such strongly negative values indicate the existence of a component within Earth’s interior that inherited its D/H ratio directly from the protosolar nebula.

Reference
Hallis LJ, Huss GR, Nagashima K, Taylor GJ, Halldórsson SA, Hilton DR, Mottl MJ, Meech KJ (2015)Evidence for primordial water in Earth’s deep mantle. Science 350, 795-797.
Link to Article [DOI: 10.1126/science.aac4834]
Reprinted with permission by AAAS