page_title: Hydrogen isotope biogeochemistry
section_title: Extraterrestrial Objects
hierarchical_section_title: Hydrogen isotope biogeochemistry / Observed variations in isotope abundance / Extraterrestrial Objects
caption_attribution_description: English: Robert, F. 2006. Solar System Deuterium/Hydrogen Ratio. Meteorites and the Early Solar System II, D. S. Lauretta and H. Y. McSween Jr. (eds.), University of Arizona Press, Tucson, 943 pp., p.341-351
context_page_description: Hydrogen isotope biogeochemistry is the scientific study of biological, geological, and chemical processes in the environment using the distribution and relative abundance of hydrogen isotopes. There are two stable isotopes of hydrogen, protium ¹H and deuterium ²H, which vary in relative abundance on the order of hundreds of permil. The ratio between these two species can be considered the hydrogen isotopic fingerprint of a substance. Understanding isotopic fingerprints and the sources of fractionation that lead to variation between them can be applied to address a diverse array of questions ranging from ecology and hydrology to geochemistry and paleoclimate reconstructions. Since specialized techniques are required to measure natural hydrogen isotope abundance ratios, the field of hydrogen isotope biogeochemistry provides uniquely specialized tools to more traditional fields like ecology and geochemistry.
context_section_description: Variations of D/H ratio in the solar system
  Earth
  The H isotope composition of mantle rocks on earth is highly variable, and that of mantle water is around −80‰ ~ −50‰ depending on its states such as fluid, hydrous phase, hydroxyl point defect, Juvenile water (from degassing of the mantle), magmatic water (water equilibrated with a magma).
  Sun
  The D/H ratio of the sun is around 21 ± 5 × 10⁻⁶.
  Mars
  The current Hydrogen isotope composition is enriched by a factor of 5 relative to terrestrial ocean water due to continual losses of H in Martian atmosphere. Therefore, the δD value is estimated to be around +4000‰.
  The D/H ratios for Jupiter and Saturn is nearly in the order of 10⁻⁵, and the D/H ratios of Uranus and Neptune is closer to the order of 10⁻⁴.
  Hydrogen is the most abundant element in the universe. Variations in isotopic composition of extraterrestrial materials stem from planetary accretion or other planetary processes such as atmospheric escape, and are larger for H and N than for C and O. The preservation of D-enrichment is observed in chondritic meteorites, interplanetary dust particles and cometary volatiles.
  From the Helium isotope abundance data, the cosmic D/H value is estimated to be around 20 ppm which is much lower than the terrestrial D/H ratio of 150 ppm. The enrichment of D/H from the proto-solar reservoir occurs for most of the planets except for Jupiter and Saturn, the massive gaseous planets. The D/H ratios of the atmospheres of Venus and Mars are ~2 × 10⁻² and ~8 × 10⁻⁴ respectively. The D/H ratios of Uranus and Neptune is larger than that of protosolar reservoir by a factor of around 3 due to their Deuterium-rich icy cores. The D/H ratios for comets are much larger than the values for the planets in the solar system with δD value of around 1000‰.
  The Hydrogen isotope compositions in the galaxy and the solar system are shown in the table.
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