The origins and concentrations of water, carbon, nitrogen and noble gases on Earth

By B. Marty. 2014

902 citations recorded by the source corpus.

Abstract The isotopic compositions of terrestrial hydrogen and nitrogen are clearly different from those of the nebular gas from which the solar system formed, and also differ from most of cometary values. Terrestrial N and H isotopic compositions are in the range of values characterizing primitive meteorites, which suggests that water, nitrogen, and other volatile elements on Earth originated from a cosmochemical reservoir that also sourced the parent bodies of primitive meteorites. Remnants of the proto-solar nebula (PSN) are still present in the mantle, presumably signing the sequestration of PSN gas at an early stage of planetary growth. The contribution of cometary volatiles appears limited to a few percents at most of the total volatile inventory of the Earth. The isotope signatures of H, N, Ne and Ar can be explained by mixing between two end-members of solar and chondritic compositions, respectively, and do not require isotopic fractionation during hydrodynamic escape of an early atmosphere. The terrestrial inventory of 40Ar (produced by the decay of 40K throughout the Earth's history) suggests that a significant fraction of radiogenic argon may be still trapped in the silicate Earth. By normalizing other volatile element abundances to this isotope, it is proposed that the Earth is not as volatile-poor as previously thought. Our planet may indeed contain up to ~ 3000 ppm water (preferred range: 1000–3000 ppm), and up to ~ 500 ppm C, both largely sequestrated in the solid Earth. This volatile content is equivalent to an ~ 2 (± 1) % contribution of carbonaceous chondrite (CI-CM) material to a dry proto-Earth, which is higher than the contribution of chondritic material advocated to account for the platinum group element budget of the mantle. Such a (relatively) high contribution of volatile-rich matter is consistent with the accretion of a few wet planetesimals during Earth accretion, as proposed by recent dynamical models. The abundance pattern of major volatile elements and of noble gases is also chondritic, with two notable exceptions. Nitrogen is depleted by one order of magnitude relative to water, carbon and most noble gases, which is consistent with either N retention in a mantle phase during magma generation, or trapping of N in the core. Xenon is also depleted by one order of magnitude, and enriched in heavy isotopes relative to chondritic or solar Xe (the so-called “xenon paradox”). This depletion and isotope fractionation might have taken place due to preferential ionization of xenon by UV light from the early Sun, either before Earth's formation on parent material, or during irradiation of the ancient atmosphere. The second possibility is consistent with a recent report of chondritic-like Xe in Archean sedimentary rocks that suggests that this process was still ongoing during the Archean eon (Pujol et al., 2011). If the depletion of Xe in the atmosphere was a long-term process that took place after the Earth-building events, then the amounts of atmospheric 129Xe and 131–136Xe, produced by the short-lived radioactivities of 129I (T1/2 = 16 Ma) and 244Pu (T1/2 = 82 Ma), respectively, need to be corrected for subsequent loss. Doing so, the I–Pu–Xe age of the Earth becomes ≤ 50 Ma after start of solar system formation, instead of ~ 120 Ma as computed with the present-day atmospheric Xe inventory.

Subfields: Astronomy and Astrophysics, Ecology

View Paper: https://www.semanticscholar.org/paper/e2a56ed52c8eae3229a1c7305c6e702939800c01

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Citations in the corpus

Planetesimal formation near the snowline: in or out? (2017, background): “The fact that the planets in the inner solar system are waterpoor (Marty 2012; McCubbin et al. 2012), even though the snowline should have migrated to 1 au before the disk was depleted, was pointed out as the “snowline problem” by Oka et al. (2011).”
Origins of volatile elements (H, C, N, noble gases) on Earth and Mars in light of recent results from the ROSETTA cometary mission (2016, positive): “In line with this, krypton (Holland et al., 2009), hydrogen and nitrogen isotopes (Alexander et al., 2012; Marty, 2012) point to a chondritic, rather than cometary, source for contributed volatiles that are now stored in the Terrestrial mantle (Fig.”
The origin of water in the primitive Moon as revealed by the lunar highlands samples (2014, background): “It is possible that the Earth–Moon system accreted volatiles from the same source (e.g., carbonaceous chondrites; Marty, 2012) and then subsequently differentiated such that their interiors were characterised by water with similar H isotopic composition.”
Origin of water in the inner Solar System: Planetesimals scattered inward during Jupiter and Saturn's rapid gas accretion (2017, background): “Estimates range from less than one ocean (Panero, 2016) to a few (Halliday, 2013) to more than ten oceans (Marty, 2012), where an “ocean” of water is defined as the amount of water on Earth’s surface (≈ 1.5 × 1024 g).”
Nitrogen solubility in molten metal and silicate at high pressure and temperature (2012, background): “5 following Marty (2012).”
A hydrogen-based oxidation mechanism relevant to planetary formation (2013, background): “Geochemical estimates, which are more generally used to constrain the source of volatiles, suggest solid earth water contents up to 13 ocean equivalents (Marty, 2012).”
A theoretical framework for volcanic degassing chemistry in a comparative planetology perspective and implications for planetary atmospheres (2014, methodology): “A C-richer mantle source, as suggested fro m a recent geochemical survey (Marty, 2012), would not modify the following conclusions, it would essentially accelerate the process we describe.”
Water delivery and giant impacts in the 'Grand Tack' scenario (2014, neutral): “(Marty, 2012).”
The Nitrogen Budget of Earth (2015, methodology): “While the exact nature and composition of planetary accretionary bodies are a matter of debate, (e.g., Marty, 2012; Halliday, 2013), some combinationof chondrite-likematerial accreted to form the rockyplanets, including Earth.”
Nitrogen Isotopes and Mantle Geodynamics: The Emergence of Life and the Atmosphere–Crust–Mantle Connection (2013, background): “On the one hand, studies of several Archaean crustal rocks (giant quartz veins) and 2.7 Ga kerogens suggest signifi cant δ15N evolution of atmospheric nitrogen, from greater than +40‰ to the present value of 0‰ (Jia and Kerrich 2004).”
The Non-carbonaceous–Carbonaceous Meteorite Dichotomy (2020, background): “These objects are the most likely source of Earth’s water and highly volatiles species (Alexander et al. 2012; Marty 2012).”
The abundance, distribution, and isotopic composition of Hydrogen in the Moon as revealed by basaltic lunar samples: Implications for the volatile inventory of the Moon (2013, background): “…2012) and impact melt breccia (Steele et al., 2010), and numerous geochemical data such as different stable isotope ratios (Robert, 2001; Alexander et al., 2012; Marty, 2012), chondritic abundances of highly siderophile elements (Day et al., 2007; Bottke et al., 2010; Dale et al., 2012) and Hf–”
Fossilized condensation lines in the Solar System protoplanetary disk (2015, neutral): “1% of water by mass (Marty, 2012).”
The solid Earth’s influence on sea level (2013, background): “Indeed, the mantle interior likely contains a volume of water that exceeds that of the surface oceans (Hirschmann and Kohlstedt, 2012), possibly by an order of magnitude (Marty, 2012).”