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Title: Formation of diamonds in laser-compressed hydrocarbons at planetary interior conditions

Abstract

The effects of hydrocarbon reactions and diamond precipitation on the internal structure and evolution of icy giant planets such as Neptune and Uranus have been discussed for more than three decades. Inside these celestial bodies, simple hydrocarbons such as methane, which are highly abundant in the atmospheres, are believed to undergo structural transitions that release hydrogen from deeper layers and may lead to compact stratified cores. Indeed, from the surface towards the core, the isentropes of Uranus and Neptune intersect a temperature–pressure regime in which methane first transforms into a mixture of hydrocarbon polymers, whereas, in deeper layers, a phase separation into diamond and hydrogen may be possible. Here in this paper, we show experimental evidence for this phase separation process obtained by in situ X-ray diffraction from polystyrene (C 8H 8) n samples dynamically compressed to conditions around 150 GPa and 5,000 K; these conditions resemble the environment around 10,000 km below the surfaces of Neptune and Uranus. Our findings demonstrate the necessity of high pressures for initiating carbon–hydrogen separation and imply that diamond precipitation may require pressures about ten times as high as previously indicated by static compression experiments. In conclusion, our results will inform mass–radius relationships ofmore » carbon-bearing exoplanets, provide constraints for their internal layer structure and improve evolutionary models of Uranus and Neptune, in which carbon–hydrogen separation could influence the convective heat transport.« less

Authors:
ORCiD logo [1];  [2];  [3]; ORCiD logo [4];  [5];  [6];  [5];  [5];  [7];  [5];  [5];  [8];  [5];  [9];  [5];  [10];  [11];  [12];  [2];  [13] more »;  [5];  [3];  [14] « less
  1. Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany); Univ. of California, Berkeley, CA (United States). Department of Physics; Technische Universitat Dresden (Germany). Institute of Solid State and Materials Physics
  2. Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany)
  3. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  4. Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany); Osaka University (Japan). Open and Transdisciplinary Research Institute
  5. SLAC National Accelerator Lab., Menlo Park, CA (United States)
  6. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Technische Universitat Darmstadt (Germany). Institut fur Kernphysik
  7. University of Warwick, Coventry (United Kingdom). Centre for Fusion, Space and Astrophysics, Department of Physics
  8. SLAC National Accelerator Lab., Menlo Park, CA (United States); Univ. of Michigan, Ann Arbor, MI (United States)
  9. SLAC National Accelerator Lab., Menlo Park, CA (United States); European XFEL GmbH, Schenefeld (Germany)
  10. GSI Helmholtzzentrum fur Schwerionenforschung GmbH, Darmstadt (Germany)
  11. Technische Universitat Darmstadt (Germany). Institut fur Kernphysik
  12. Univ. of California, Berkeley, CA (United States). Department of Physics
  13. SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., CA (United States). Department of Physics
  14. Univ. of California, Berkeley, CA (United States). Department of Physics; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24); USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1393331
Alternate Identifier(s):
OSTI ID: 1476528
Report Number(s):
LLNL-JRNL-707514
Journal ID: ISSN 2397-3366; PII: 219
Grant/Contract Number:  
AC52-07NA27344; AC02-76SF00515; FG52-10NA29649; NA0001859; AC02-05CH11231
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nature Astronomy
Additional Journal Information:
Journal Volume: 1; Journal Issue: 9; Journal ID: ISSN 2397-3366
Publisher:
Springer
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; Core processes; Giant planets; Phase transitions and critical phenomena

Citation Formats

Kraus, D., Vorberger, J., Pak, A., Hartley, N. J., Fletcher, L. B., Frydrych, S., Galtier, E., Gamboa, E. J., Gericke, D. O., Glenzer, S. H., Granados, E., MacDonald, M. J., MacKinnon, A. J., McBride, E. E., Nam, I., Neumayer, P., Roth, M., Saunders, A. M., Schuster, A. K., Sun, P., van Driel, T., Döppner, T., and Falcone, R. W.. Formation of diamonds in laser-compressed hydrocarbons at planetary interior conditions. United States: N. p., 2017. Web. doi:10.1038/s41550-017-0219-9.
Kraus, D., Vorberger, J., Pak, A., Hartley, N. J., Fletcher, L. B., Frydrych, S., Galtier, E., Gamboa, E. J., Gericke, D. O., Glenzer, S. H., Granados, E., MacDonald, M. J., MacKinnon, A. J., McBride, E. E., Nam, I., Neumayer, P., Roth, M., Saunders, A. M., Schuster, A. K., Sun, P., van Driel, T., Döppner, T., & Falcone, R. W.. Formation of diamonds in laser-compressed hydrocarbons at planetary interior conditions. United States. doi:10.1038/s41550-017-0219-9.
Kraus, D., Vorberger, J., Pak, A., Hartley, N. J., Fletcher, L. B., Frydrych, S., Galtier, E., Gamboa, E. J., Gericke, D. O., Glenzer, S. H., Granados, E., MacDonald, M. J., MacKinnon, A. J., McBride, E. E., Nam, I., Neumayer, P., Roth, M., Saunders, A. M., Schuster, A. K., Sun, P., van Driel, T., Döppner, T., and Falcone, R. W.. Mon . "Formation of diamonds in laser-compressed hydrocarbons at planetary interior conditions". United States. doi:10.1038/s41550-017-0219-9. https://www.osti.gov/servlets/purl/1393331.
@article{osti_1393331,
title = {Formation of diamonds in laser-compressed hydrocarbons at planetary interior conditions},
author = {Kraus, D. and Vorberger, J. and Pak, A. and Hartley, N. J. and Fletcher, L. B. and Frydrych, S. and Galtier, E. and Gamboa, E. J. and Gericke, D. O. and Glenzer, S. H. and Granados, E. and MacDonald, M. J. and MacKinnon, A. J. and McBride, E. E. and Nam, I. and Neumayer, P. and Roth, M. and Saunders, A. M. and Schuster, A. K. and Sun, P. and van Driel, T. and Döppner, T. and Falcone, R. W.},
abstractNote = {The effects of hydrocarbon reactions and diamond precipitation on the internal structure and evolution of icy giant planets such as Neptune and Uranus have been discussed for more than three decades. Inside these celestial bodies, simple hydrocarbons such as methane, which are highly abundant in the atmospheres, are believed to undergo structural transitions that release hydrogen from deeper layers and may lead to compact stratified cores. Indeed, from the surface towards the core, the isentropes of Uranus and Neptune intersect a temperature–pressure regime in which methane first transforms into a mixture of hydrocarbon polymers, whereas, in deeper layers, a phase separation into diamond and hydrogen may be possible. Here in this paper, we show experimental evidence for this phase separation process obtained by in situ X-ray diffraction from polystyrene (C8H8) n samples dynamically compressed to conditions around 150 GPa and 5,000 K; these conditions resemble the environment around 10,000 km below the surfaces of Neptune and Uranus. Our findings demonstrate the necessity of high pressures for initiating carbon–hydrogen separation and imply that diamond precipitation may require pressures about ten times as high as previously indicated by static compression experiments. In conclusion, our results will inform mass–radius relationships of carbon-bearing exoplanets, provide constraints for their internal layer structure and improve evolutionary models of Uranus and Neptune, in which carbon–hydrogen separation could influence the convective heat transport.},
doi = {10.1038/s41550-017-0219-9},
journal = {Nature Astronomy},
number = 9,
volume = 1,
place = {United States},
year = {Mon Aug 21 00:00:00 EDT 2017},
month = {Mon Aug 21 00:00:00 EDT 2017}
}

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Works referenced in this record:

Decomposition of hydrocarbons to hydrogen and carbon
journal, May 2009

  • Ahmed, Shakeel; Aitani, Abdullah; Rahman, Faizur
  • Applied Catalysis A: General, Vol. 359, Issue 1-2, p. 1-24
  • DOI: 10.1016/j.apcata.2009.02.038