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Atomic-scale mixing between MgO and H2O in the deep interiors of water-rich planets

Nature Astronomy volume 5, pages 815–821 (2021)Cite this article

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Abstract

Water-rich planets exist in our Solar System (Uranus and Neptune) and are found to be common in the extrasolar systems (some of the sub-Neptunes). In conventional models of these planets a thick water-rich layer is underlain by a separate rocky interior. Here we report experimental results on two rock-forming minerals, olivine ((Mg,Fe)2SiO4) and ferropericlase ((Mg,Fe)O), in water at the pressure and temperature conditions expected for the water-rich planets. Our data indicate a selective leaching of MgO, which peaks between 20 and 40 GPa and above 1,500 K. For water-rich planets with 1–6 Earth masses (>50 wt% H2O), the chemical reaction at the deep water–rock interface would lead to high concentrations of MgO in the H2O layer. For Uranus and Neptune, the top ~3% of the H2O layer would have a large storage capacity for MgO. If an early dynamic process enables the rock–H2O reaction, the topmost H2O layer may be rich in MgO, possibly affecting the thermal history of the planet.

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Fig. 1: X-ray diffraction patterns measured during laser-heating experiments.
Fig. 2: SEM analysis of the recovered sample from laser heating of the olivine starting material in H2O medium.
Fig. 3: Intensities of ferropericlase peaks as a function of pressure and temperature.
Fig. 4: Preliminary models of the water-rich planetary interiors.

Data availability

All X-ray diffraction, IR spectra and SEM–energy-dispersive X-ray spectroscopy data supporting this study are available at https://doi.org/10.5281/zenodo.4632916 or by contacting the corresponding authors.

Code availability

Python scripts used to analyse the X-ray diffraction data supporting this study are available from https://github.com/SHDShim/PeakPo.

References

  1. Dziewonski, A. M. & Anderson, D. L. Preliminary reference Earth model. Phys. Earth Planet. Inter. 25, 297–356 (1981).

    Article  ADS  Google Scholar 

  2. Stixrude, L. & Lithgow-Bertelloni, C. Geophysics of chemical heterogeneity in the mantle. Annu. Rev. Earth Planet. Sci. 40, 569–595 (2012).

    Article  ADS  Google Scholar 

  3. Hirose, K., Labrosse, S. & Hernlund, J. Composition and state of the core. Annu. Rev. Earth Planet. Sci. 41, 657–691 (2013).

    Article  ADS  Google Scholar 

  4. Thompson, S. E. et al. Planetary candidates observed by Kepler. VIII. A fully automated catalog with measured completeness and reliability based on Data Release 25. Astrophys. J. Suppl. Ser. 235, 38 (2018).

    Article  ADS  Google Scholar 

  5. Hsu, D. C., Ford, E. B., Ragozzine, D. & Ashby, K. Occurrence rates of planets orbiting FGK stars: combining Kepler DR25, Gaia DR2, and Bayesian inference. Astron. J. 158, 109 (2019).

    Article  ADS  Google Scholar 

  6. Zeng, L. et al. Growth model interpretation of planet size distribution. Proc. Natl Acad. Sci. USA 116, 9723–9728 (2019).

    Article  ADS  Google Scholar 

  7. Batalha, N. M. Exploring exoplanet populations with NASA’s Kepler Mission. Proc. Natl Acad. Sci. USA 111, 12647–12654 (2014).

    Article  ADS  Google Scholar 

  8. Léger, A. et al. A new family of planets? ‘Ocean-Planets’. Icarus 169, 499–504 (2004).

    Article  ADS  Google Scholar 

  9. Redmer, R., Mattsson, T. R., Nettelmann, N. & French, M. The phase diagram of water and the magnetic fields of Uranus and Neptune. Icarus 211, 798–803 (2011).

    Article  ADS  Google Scholar 

  10. Guillot, T. The interiors of giant planets: models and outstanding questions. Annu. Rev. Earth Planet. Sci. 33, 493–530 (2005).

    Article  ADS  Google Scholar 

  11. Ohtani, E. Hydrous minerals and the storage of water in the deep mantle. Chem. Geol. 418, 6–15 (2015).

    Article  ADS  Google Scholar 

  12. Hanel, R. et al. Infrared observations of the Uranian system. Science 233, 70–74 (1986).

    Article  ADS  Google Scholar 

  13. Pearl, J. C., Conrath, B. J., Hanel, R. A. & Pirraglia, J. A. The albedo, effective temperature, and energy balance of Uranus, as determined from Voyager IRIS data. Icarus 84, 12–28 (1990).

    Article  ADS  Google Scholar 

  14. Spiegel, D. S., Fortney, J. J. & Sotin, C. Structure of exoplanets. Proc. Natl Acad. Sci. USA 111, 12622–12627 (2014).

    Article  ADS  Google Scholar 

  15. Helled, R., Nettelmann, N. & Guillot, T. Uranus and Neptune: origin, evolution and internal structure. Space Sci. Rev. 216, 38 (2020).

    Article  ADS  Google Scholar 

  16. Shieh, S. R., Mao, H.-K., Hemley, R. J. & Ming, L. C. Decomposition of phase D in the lower mantle and the fate of dense hydrous silicates in subducting slabs. Earth Planet. Sci. Lett. 159, 13–23 (1998).

    Article  ADS  Google Scholar 

  17. Tsuchiya, J. First principles prediction of a new high-pressure phase of dense hydrous magnesium silicates in the lower mantle. Geophys. Res. Lett. 40, 4570–4573 (2013).

    Article  ADS  Google Scholar 

  18. Nishi, M. et al. Stability of hydrous silicate at high pressures and water transport to the deep lower mantle. Nat. Geosci. 7, 224–227 (2014).

    Article  ADS  Google Scholar 

  19. Ohtani, E., Amaike, Y., Kamada, S., Sakamaki, T. & Hirao, N. Stability of hydrous phase H MgSiO4H2 under lower mantle conditions. Geophys. Res. Lett. 41, 8283–8287 (2014).

    Article  ADS  Google Scholar 

  20. Rietveld, H. M. A profile refinement method for nuclear and magnetic structures. J. Appl. Crystallogr. 2, 65–71 (1969).

    Article  Google Scholar 

  21. Gleason, A. E., Jeanloz, R. & Kunz, M. Pressure-temperature stability studies of FeOOH using X-ray diffraction. Am. Mineral. 93, 1882–1885 (2008).

    Article  ADS  Google Scholar 

  22. Fei, Y. & Mao, H.-K. Static compression of Mg(OH)2 to 78 GPa at high temperature and constraints on the equation of state of fluid H2O. J. Geophys. Res. Solid Earth 98, 11875–11884 (1993).

    Article  Google Scholar 

  23. Fukui, H. et al. Decomposition of brucite up to 20 GPa: evidence for high MgO-solubility in the liquid phase. Eur. J. Mineral. 17, 261–267 (2005).

    Article  ADS  Google Scholar 

  24. Stalder, R., Ulmer, P., Thompson, A. B. & Günther, D. High pressure fluids in the system MgO-SiO2-H2O under upper mantle conditions. Contrib. Mineral. Petrol. 140, 607–618 (2001).

    Article  ADS  Google Scholar 

  25. Schwager, B. & Boehler, R. H2O: another ice phase and its melting curve. High Press. Res. 28, 431–433 (2008).

    Article  ADS  Google Scholar 

  26. Lin, J.-F. et al. Melting behavior of H2O at high pressures and temperatures. Geophys. Res. Lett. 32, L11306 (2005).

  27. Gillon, M. et al. Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1. Nature 542, 456–460 (2017).

    Article  ADS  Google Scholar 

  28. Unterborn, C. T., Desch, S. J., Hinkel, N. R. & Lorenzo, A. Inward migration of the TRAPPIST-1 planets as inferred from their water-rich compositions. Nat. Astron. 2, 297–302 (2018).

    Article  ADS  Google Scholar 

  29. Charbonneau, D. et al. A super-Earth transiting a nearby low-mass star. Nature 462, 891–894 (2009).

    Article  ADS  Google Scholar 

  30. Nettelmann, N., Fortney, J. J., Kramm, U. & Redmer, R. Thermal evolution and structure models of the transiting super-Earth GJ 1214b. Astrophys. J. 733, 2 (2011).

  31. Leconte, J., Selsis, F., Hersant, F. & Guillot, T. Condensation-inhibited convection in hydrogen-rich atmospheres. Astron. Astrophys. 598, A98 (2017).

  32. Sarafian, E., Gaetani, G. A., Hauri, E. H. & Sarafian, A. R. Experimental constraints on the damp peridotite solidus and oceanic mantle potential temperature. Science 355, 942–945 (2017).

  33. Hamano, K., Abe, Y. & Genda, H. Emergence of two types of terrestrial planet on solidification of magma ocean. Nature 497, 607–610 (2013).

  34. Shen, A. H. & Keppler, H. Direct observation of complete miscibility in the albite–H2O system. Nature 385, 710–712 (1997).

    Article  ADS  Google Scholar 

  35. Newton, R. C. & Manning, C. E. Thermodynamics of SiO2–H2O fluid near the upper critical end point from quartz solubility measurements at 10 kbar. Earth Planet. Sci. Lett. 274, 241–249 (2008).

    Article  ADS  Google Scholar 

  36. Ni, H. et al. Distribution, cycling and impact of water in the Earth’s interior. Natl Sci. Rev. 4, 879–891 (2017).

    Article  Google Scholar 

  37. Hirschmann, M. M., Aubaud, C. & Withers, A. C. Storage capacity of H2O in nominally anhydrous minerals in the upper mantle. Earth Planet. Sci. Lett. 236, 167–181 (2005).

  38. Nettelmann, N. et al. Uranus evolution models with simple thermal boundary layers. Icarus 275, 107–116 (2016).

    Article  ADS  Google Scholar 

  39. Podolak, M., Helled, R. & Schubert, G. Effect of non-adiabatic thermal profiles on the inferred compositions of Uranus and Neptune. Mon. Not. R. Astron. Soc. 487, 2653–2664 (2019).

  40. Vazan, A. & Helled, R. Explaining the low luminosity of Uranus: a self-consistent thermal and structural evolution. Astron. Astrophys. 633, A50 (2020).

    Article  ADS  Google Scholar 

  41. Nettelmann, N., Helled, R., Fortney, J. J. & Redmer, R. New indication for a dichotomy in the interior structure of Uranus and Neptune from the application of modified shape and rotation data. Planet. Space Sci. 77, 143–151 (2013).

  42. Kegerreis, J. A. et al. Consequences of giant impacts on early Uranus for rotation, internal structure, debris, and atmospheric erosion. Astrophys. J. 861, 52 (2018).

    Article  ADS  Google Scholar 

  43. Vazan, A. et al. A new perspective on interiors of ice-rich planets: ice–rock mixture rather than a layered structure. Preprint at https://arxiv.org/abs/2011.00602 (2020).

  44. Sun, J., Clark, B. K., Torquato, S. & Car, R. The phase diagram of high-pressure superionic ice. Nat. Commun. 6, 8156 (2015).

  45. Marquardt, H. et al. Elastic shear anisotropy of ferropericlase in Earth’s lower mantle. Science 324, 224–226 (2009).

    Article  ADS  Google Scholar 

  46. Dorogokupets, P. I. & Dewaele, A. Equations of state of MgO, Au, Pt, NaCl-B1, and NaCl-B2: internally consistent high-temperature pressure scales. High Press. Res. 27, 431–446 (2007).

    Article  ADS  Google Scholar 

  47. Shim, S.-H. PeakPo—a python software for X-ray diffraction analysis at high pressure and high temperature v.7.2.2 (Zenodo, 2017); https://doi.org/10.5281/zenodo.810200

  48. Prakapenka, V. B. et al. Advanced flat top laser heating system for high pressure research at GSECARS: application to the melting behavior of germanium. High Press. Res. 28, 225–235 (2008).

    Article  ADS  Google Scholar 

  49. Liermann, H.-P. et al. The Extreme Conditions Beamline P02.2 and the Extreme Conditions Science Infrastructure at PETRA III. J. Synchrotron Radiat. 22, 908–924 (2015).

    Article  Google Scholar 

  50. Lin, J.-F. et al. High pressure–temperature Raman measurements of H2O melting to 22 GPa and 900 K. J. Chem. Phys. 121, 8423 (2004).

    Article  ADS  Google Scholar 

  51. Schwager, B., Chudinovskikh, L., Gavriliuk, A. & Boehler, R. Melting curve of H2O to 90 GPa measured in a laser-heated diamond cell. J. Phys. Condens. Matter 16, S1177–S1179 (2004).

  52. Prescher, C. & Prakapenka, V. B. Dioptas: a program for reduction of two-dimensional X-ray diffraction data and data exploration. High Press. Res. 35, 223–230 (2015).

    Article  ADS  Google Scholar 

  53. Boehler, R. High-pressure experiments and the phase diagram of lower mantle and core materials. Rev. Geophys. 38, 221–245 (2000).

    Article  ADS  Google Scholar 

  54. Shen, G., Rivers, M. L., Wang, Y. & Sutton, S. R. Laser heated diamond cell system at the Advanced Photon Source for in situ x-ray measurements at high pressure and temperature. Rev. Sci. Instrum. 72, 1273–1282 (2001).

  55. Benedetti, L. R. & Loubeyre, P. Temperature gradients, wavelength-dependent emissivity, and accuracy of high and very-high temperatures measured in the laser-heated diamond cell. High Press. Res. 24, 423–445 (2004).

    Article  ADS  Google Scholar 

  56. Mao, H. K., Xu, J. & Bell, P. M. Calibration of the ruby pressure gauge to 800 kbar under quasi-hydrostatic conditions. J. Geophys. Res. Solid Earth 91, 4673–4676 (1986).

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Acknowledgements

This work was supported by the Leader Researcher programme (NRF-2018R1A3B1052042) of the Korean Ministry of Science and ICT (MSIT). We also acknowledge the support by grant NRF-2019K1A3A7A09033395 of the MSIT. S.-H.S. was supported by NSF grant EAR1338810 and National Aeronautics and Space Administration (NASA) grant 80NSSC18K0353. S.-H.S. also benefited from collaborations and information exchange within the Nexus for Exoplanet System Science (NExSS) research coordination network sponsored by NASA’s Science Mission Directorate. S.S. acknowledges support by the GFZ German Research Centre for Geosciences. This research used resources of the Advanced Photon Source, a US Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. We acknowledge the support of GSECARS (Sector 13), which is supported by the National Science Foundation—Earth Sciences (EAR-1634415), and the Department of Energy, Geosciences (DE-FG02-94ER14466). Parts of this research were carried out at the P02.2 beamline at PETRA III, and we acknowledge Deutsches Elektronen-Synchrotron (DESY, Hamburg, Germany), a member of the Helmholtz Association HGF, for the provision of experimental facilities. We also acknowledge the scientific exchange and support of the Center for Molecular Water Science (CMWS) at DESY. This research also used beamline 22-IR-1 of the National Synchrotron Light Source II, a US DOE Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under contract DE-SC0012704 and COMPRES under NSF cooperative agreement EAR 11-57758 and CDAC (DE-FC03-03N00144).

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Authors and Affiliations

  1. Department of Earth System Sciences, Yonsei University, Seoul, South Korea

    Taehyun Kim & Yongjae Lee

  2. Center for Advanced Radiation Sources, The University of Chicago, Argonne, IL, USA

    Stella Chariton & Vitali Prakapenka

  3. Photon Sciences, Deutsches Elektronen Synchrotron, Hamburg, Germany

    Anna Pakhomova & Hanns-Peter Liermann

  4. Department of Physics, University of Illinois at Chicago, Chicago, IL, USA

    Zhenxian Liu

  5. GFZ German Research Centre for Geosciences, Potsdam, Germany

    Sergio Speziale

  6. School of Earth and Space Exploration, Arizona State University, Tempe, AZ, USA

    Sang-Heon Shim

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Contributions

T.K. performed the experiments and analysed the data with help from S.-H.S. and S.C. V.P., A.P. and H.-P.L. helped with synchrotron beamline set-up and operation. S.S. provided the samples. Y.L. and S.-H.S. conceptualized the research, discussed the results with T.K. and worked on the manuscript with all authors.

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Correspondence to Sang-Heon Shim or Yongjae Lee.

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The authors declare no competing interests.

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Peer review information Nature Astronomy thanks Stéphane Mazevet and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Information

Supplementary Sections 1–7, Figs. 1–7 and Table 1.

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Kim, T., Chariton, S., Prakapenka, V. et al. Atomic-scale mixing between MgO and H2O in the deep interiors of water-rich planets. Nat Astron 5, 815–821 (2021). https://doi.org/10.1038/s41550-021-01368-2

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