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Licensed Unlicensed Requires Authentication Published by De Gruyter January 3, 2017

Carbon as the dominant light element in the lunar core

Edgar S. Steenstra, Yanhao Lin, Nachiketa Rai, Max Jansen and Wim van Westrenen
From the journal American Mineralogist


Geophysical and geochemical observations point to the presence of a light element in the lunar core, but the exact abundance and type of light element are poorly constrained. Accurate constraints on lunar core composition are vital for models of lunar core dynamo onset and demise, core formation conditions (e.g., depth of the lunar magma ocean or LMO) and therefore formation conditions, as well as the volatile inventory of the Moon. A wide range of previous studies considered S as the dominant light element in the lunar core. Here, we present new constraints on the composition of the lunar core, using mass-balance calculations, combined with previously published models that predict the metal–silicate partitioning behavior of C, S, Ni, and recently proposed new bulk silicate Moon (BSM) abundances of S and C. We also use the bulk Moon abundance of C and S to assess the extent of their devolatilization. We observe that the Ni content of the lunar core becomes unrealistically high if shallow (<3 GPa) LMO scenarios are assumed, and therefore only deeper (>3 GPa) LMO scenarios are considered for S and C. The moderately siderophile metal–silicate partitioning behavior of S during lunar core formation, combined with the low BSM abundance of S, yields only <0.16 wt% S in the core, virtually independent of the pressure (P) and temperature (T) conditions during core formation. Instead, our analysis suggests that C is the dominant light element in the lunar core. The siderophile behavior of C during lunar core formation results in a core C content of ~0.6–4.8 wt%, with the exact amount depending on the core formation conditions. A C-rich lunar core could explain (1) the existence of a present-day molten outer core, (2) the estimated density of the lunar outer core, and (3) the existence of an early lunar core dynamo driven by compositional buoyancy due to core crystallization. Finally, our calculations suggest the C content of the bulk Moon is close to its estimated abundance in the bulk silicate Earth (BSE), suggesting more limited volatile loss during the Moon-forming event than previously thought.


We acknowledge the constructive feedback from two anonymous reviewers, and thank H. Watson for her editorial handling of the manuscript. This study was funded by a Netherlands Organisation for Scientific Research (NWO) Vici grant to W.v.W. We acknowledge fruitful discussions with P. Kaskes and S. de Graaff. We also thank A. Boujibar for providing calculation details of her published work. E.S.S. thanks the Planetary Science Institute (PSI) for financial support through the 2015 Pierazzo International Student Travel Award.


Antonangeli, D., Morard, G., Schmerr, N.C., Komabayashi, T., Krisch, M., Fiquet, G., and Fei, Y. (2015) Towards a mineral physics reference model for the Moon’s core. Proceedings of the National Academy of Sciences, 112, 3916–3919.10.1073/pnas.1417490112Search in Google Scholar

Bombardieri, D.J., Norman, M.D., Kamenetsky, V.S., and Danyushevsky, L.V. (2005) Major element and primary sulfur concentrations in Apollo 12 mare basalts: The view from melt inclusions. Meteoritic and Planetary Science, 40, 679–693.10.1111/j.1945-5100.2005.tb00973.xSearch in Google Scholar

Boujibar, A., Andrault, D., Bouhifd, M.A., Bolfan–Casanova, N., Devidal, J.-L., and Trcera, N. (2014) Metal–silicate partitioning of sulphur, new experimental and thermodynamic constraints on planetary accretion. Earth and Planetery Science Letters, 391, 42–54.10.1016/j.epsl.2014.01.021Search in Google Scholar

Buono, A.S., and Walker, D. (2011) The Fe–rich liquidus in the Fe–FeS system from 1 bar to 10 GPa. Geochimica et Cosmochimica Acta, 75, 2072–2087.10.1016/j.gca.2011.01.030Search in Google Scholar

Canup, R.M. (2004) Simulations of a late lunar-forming impact. Icarus, 168, 433–456.10.1016/j.icarus.2003.09.028Search in Google Scholar

Chabot, N.L., Campbell, A.J., McDonough, W.F., Draper, D.S., Agee, C.B., Humayun, M., Watson, H.C., Cotrell, E., and Saslow, S.A. (2008) The Fe–C system at 5 GPa and implications for Earth’s core. Geochimica et Cosmochimica Acta, 72, 4146–4158.10.1016/j.gca.2008.06.006Search in Google Scholar

Chen, Y., Zhang, Y., Liu, Y., Guan, Y., Eiler, J., and Stolper, E.M. (2015) Water, fluorine, and sulfur concentrations in the lunar mantle. Earth and Planetary Science Letters, 427, 37–46.10.1016/j.epsl.2015.06.046Search in Google Scholar

Chi, H., Dasgupta, R., Duncan, M.S., and Shimizu, N. (2014) Partitioning of carbon between Fe–rich alloy melt and silicate melt in a magma ocean-implications for the abundance and origin of volatiles in Earth, Mars, and the Moon. Geochimica et Cosmochimica Acta, 139, 447–471.10.1016/j.gca.2014.04.046Search in Google Scholar

Cisowski, S.M., Collinson, D.W., Runcorn, S.K., and Stephenson, A. (1983) A review of lunar paleointensity data and implications for the origin of lunar magnetism. Journal of Geophysical Research, 88, A691–A704.10.1029/JB088iS02p0A691Search in Google Scholar

Collinson, D.W. (1993) Magnetism of the Moon–A lunar core dynamo or impact magnetization? Surveys in Geophysics, 14, 89–118.10.1007/BF01044078Search in Google Scholar

Dasgupta, R., Chi, H., Shimizu, N., Buono, A.S., and Walker, D. (2013) Carbon solution and partitioning between metallic and silicate melts in a shallow magma ocean: Implications for the origin and distribution of terrestrial carbon. Geochimica et Cosmochimca Acta, 102, 191–212.10.1016/j.gca.2012.10.011Search in Google Scholar

de Meijer, R.J., Anisichkin, V.F., and van Westrenen, W. (2013) Forming the Moon from terrestrial silicate–rich material. Chemical Geology, 345, 40–49.10.1016/j.chemgeo.2012.12.015Search in Google Scholar

Delano, J.W. (1986) Abundances of cobalt, nickel, and volatiles in the silicate portion of the Moon. In W.K. Hartmann, R.J. Phillips, and G.J. Taylor, Eds., Origin of the Moon, p. 231–248. Lunar and Planetary Institute, Houston.Search in Google Scholar

Elkins-Tanton, L.T., Burgess, S., and Yin, Q.-Z. (2011) The lunar magma ocean: Reconciling the solidification process with lunar petrology and geochronology. Earth and Planetary Science Letters, 304, 326–336.10.1016/j.epsl.2011.02.004Search in Google Scholar

Garcia, R.F., Gagnepain-Beyneix, J., Chevrot, S., and Lognonné, P. (2011) Very preliminary reference Moon model. Physics of the Earth and Planetary Interiors, 202–203, 89–91.10.1016/j.pepi.2011.06.015Search in Google Scholar

——— (2012) Erratum to “Very preliminary reference Moon model.” Physics of the Earth and Planetary Interiors, 202-203, 89–91.Search in Google Scholar

Hauck, S.A., Aurnou, J.M., and Dombard A.J. (2006) Sulfur’s impact on core evolution and magnetic field generation on Ganymede. Journal of Geophysical Research: Planets, 111, E09008, 10.1029/2005JE002557.Search in Google Scholar

Hauri, E.H., Saal, A.E., Rutherford, M.J., and van Orman, J.A. (2015) Water in the Moon’s interior: Truth and consequences. Earth and Planetary Science Letters, 409, 252–264.10.1016/j.epsl.2014.10.053Search in Google Scholar

Jing, Z., Wang, Y., Kono, Y., Yu, T., Sakamaki, T., Park, C., Rivers, M.L., Sutton, S.R., and Shen, G. (2014) Sound velocity of Fe–S liquids at high pressure: Implications for the Moon’s molten outer core. Earth and Planetary Science Letters, 396, 78–87.10.1016/j.epsl.2014.04.015Search in Google Scholar

Killburn, M.R., and Wood, B.J. (1997) Metal–silicate partitioning and the incompatibility of S and Si during core formation. Earth and Planetary Science Letters, 152, 139–148.10.1016/S0012-821X(97)00125-8Search in Google Scholar

Laneuville, M., Wieczorek, M.A., Breuer, D., and Tosi, N. (2013) Asymmetric thermal evolution of the Moon. Journal of Geophysical Research: Planets, 118, 1435–1452.10.1002/jgre.20103Search in Google Scholar

Laneuville, M., Wieczorek, M.A., Breuer, D., Aubert, J., Morard, G., and Rückriemen, T. (2014) A long–lived lunar dynamo powered by core crystallization. Earth and Planetary Science Letters, 401, 251–260.10.1016/j.epsl.2014.05.057Search in Google Scholar

Li, Y., Dasgupta, R., and Tsuno, K. (2015) The effects of sulfur, silicon, water, and oxygen fugacity on carbon solubility and partitioning in Fe–rich alloy and silicate melt systems at 3 GPa and 1600° C: Implications for core–mantle differentiation and degassing of magma oceans and reduced planetary mantles. Earth and Planetary Science Letters, 415, 54–66.10.1016/j.epsl.2015.01.017Search in Google Scholar

Marty, B. (2012) The origins and concentrations of water, carbon, nitrogen and noble gases on Earth. Earth and Planetary Science Letters, 313–314, 56–66.10.1016/j.epsl.2011.10.040Search in Google Scholar

McDonough, W.F., and Sun, S.-s. (1995) The composition of the Earth. Chemical Geology, 120, 223–253.10.1016/S0074-6142(01)80077-2Search in Google Scholar

Nakajima, M., and Stevenson, D.J. (2014) Investigation of the initial state of the Moon-forming disk: bridging SPH simulations and hydrostatic models. Icarus, 233, 259–267.10.1016/j.icarus.2014.01.008Search in Google Scholar

Nakamura, Y., Lammlein, D., Latham, G., Ewing, M., Dorman, J., Press, F., and Toksöz, N. (1973) New seismic data on state of deep lunar interior. Science, 181, 49–51.10.1126/science.181.4094.49Search in Google Scholar

Rai, N., and van Westrenen, W. (2014) Lunar core formation: New constraints from metal–silicate partitioning of siderophile elements. Earth and Planetary Science Letters, 388, 343–352.10.1016/j.epsl.2013.12.001Search in Google Scholar

Ricolleau, A., Fei, Y., Corgne, A., Siebert, J., and Badro, J. (2011) Oxygen and silicon contents of the Earth’s core from high pressure metal–silicate partitioning experiments. Earth and Planetary Science Letters, 310, 409–421.10.1016/j.epsl.2011.08.004Search in Google Scholar

Righter, K. (2002) Does the Moon have a metallic core?: Constraints from Giant Impact Modeling and siderophile elements. Icarus, 158, 1–13.10.1006/icar.2002.6859Search in Google Scholar

Sanloup, C., van Westrenen, W., Dasgupta, R., Maynard-Casely, H., and Perrillat, J.-P. (2011) Compressibility change in iron-rich melt and implications for core formation models. Earth and Planetary Science Letters, 306, 118–122.10.1016/j.epsl.2011.03.039Search in Google Scholar

Shea, E.K., Weiss, B.P., Cassata, W.S., Shuster, D.L., Tikoo, S.M., Gattacceca, J., Grove, T.L., and Fuller, M.D. (2012) A long-lived lunar core dynamo. Science, 335, 453–456.10.1126/science.1215359Search in Google Scholar

Shimoyama, Y., Terasaki, H., Ohtani, E., Urakawa, S., Takubo, Y., Nishida, K., Suzuki, A., and Katayama, Y. (2013) Density of Fe–3.5 wt.% C liquid at high pressure and temperature and the effect of carbon on the density of the molten iron. Physics of the Earth and Planetary Interiors, 224, 77–82.10.1016/j.pepi.2013.08.003Search in Google Scholar

Steenstra, E.S., Knibbe, J.S., Rai, N., and van Westrenen, W. (2016a) Constraints on core formation in Vesta from metal–silicate partitioning of siderophile elements. Geochimica et Cosmochimica Acta, 177, 48–61.10.1016/j.gca.2016.01.002Search in Google Scholar

Steenstra, E.S., Rai, N., Knibbe, J.S., Lin, Y.H., and van Westrenen, W. (2016b) New geochemical models of core formation in the Moon from the metal–silicate partitioning of 15 siderophile elements. Earth and Planetary Science Letters, 441, 1–9.10.1016/j.epsl.2016.02.028Search in Google Scholar

Suckale, J., Elkins-Tanton, L.T., and Sethian, J.A. (2012) Crystals stirred up: 2. Numerical insights into the formation of the earliest crust on the Moon. Journal of Geophysical Research, 117, E08005.10.1029/2012JE004067Search in Google Scholar

Weber, R.C., Lin, P-Y., Garnero, E.J., Williams, Q., and Lognonné, P. (2011) Seismic Detection of the Lunar Core. Science, 331, 309–312.10.1126/science.1199375Search in Google Scholar

Wetzel, D.T., Hauri, E.H., Saal, A.E., and Rutherford, M.J. (2015) Carbon content and degassing history of the lunar volcanic glasses. Nature Geoscience, 8, 755–758.10.1038/ngeo2511Search in Google Scholar

Wing, B.A., and Farquhar, J. (2015) Sulfur isotope homogeneity of lunar mare basalts. Geochimica et Cosmochimica Acta, 170, 266–280.10.1016/j.gca.2015.09.003Search in Google Scholar

Yamada, Y., Matsumoto, K., Kikuchi, F., and Sasaki, S. (2014) Error determination of lunar interior structure by lunar geodetic data on seismic restriction. Physics of the Earth and Planetary Interiors, 231, 56–64.10.1016/j.pepi.2014.02.005Search in Google Scholar

Zhang, N., Parmentier, E.M., and Liang, Y. (2013) A 3-D numerical study of the thermal evolution of the Moon after cumulate mantle overturn: The importance of rheology and core solidification. Journal of Geophysical Research: Planets, 118, 1789–1804.10.1002/jgre.20121Search in Google Scholar

Received: 2016-2-18
Accepted: 2016-8-23
Published Online: 2017-1-3
Published in Print: 2017-1-1

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