The Late Asteroidal and Cometary Bombardment of Earth as Recorded in Water Deuterium to Protium Ratio

  title={The Late Asteroidal and Cometary Bombardment of Earth as Recorded in Water Deuterium to Protium Ratio},
  author={Nicolas Dauphas and François Robert and Bernard Marty},
The deuterium to protium (D/H) ratio of the deep mantle may be a remnant of the hydrogen isotopic composition of Earth forming planetesimals, which later evolved as a result of the late accretion of asteroids and comets. If so, the mass of asteroids and comets incident on Earth since the time of its accretion is estimated to be 4×1020–2×1022 kg. The combined use of water D/H ratios, the lunar cratering record, and terrestrial mantle siderophiles would favor a rather low mass fraction of comets… 

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