Research ArticleSPACE SCIENCE

Early formation of the Moon 4.51 billion years ago

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Science Advances  11 Jan 2017:
Vol. 3, no. 1, e1602365
DOI: 10.1126/sciadv.1602365
  • Fig. 1 Concordia diagram of the Apollo 14 zircons used to determine Hf model ages.

    U-Pb ID-TIMS analyses of zircon leachate (empty ellipses) and analyses of the remaining zircon residues after step leaching (filled ellipses). Ellipses are color-coded for samples.

  • Fig. 2 Magnitude of the neutron capture effect on Apollo zircons as shown by the shift in 178Hf/177Hf.

    The shift is expressed as a deviation in ε178Hfs from the terrestrial value (56). Samples with a large offset in ε178Hf all come from soil 14163 that experienced longer cosmic ray exposure on the near surface of the Moon.

  • Fig. 3 Plot of ε176HfCHUR versus 207Pb/206Pb zircon age (Gy).

    ε176HfCHUR is evaluated by the difference between initial ε176Hf(t) and the Hf isotopic composition of CHUR at time t (26). Taylor et al. (20) reported the data before and after neutron capture (NC) correction.

  • Fig. 4 Hf model age (Gy) calculated for a Lu/Hfsource = 0 as a function of 207Pb/206Pb zircon crystallization age (Gy).

    Ranges of previously proposed ages for the Moon’s formation are also shown.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/1/e1602365/DC1

    fig. S1. 176Hf/177Hf ratios normalized to the expected (present-day) value for standard zircons versus the magnitude of the peak stripping due to interfering Yb, measured as 173Yb+/177Hf +.

    fig. S2. Initial 176Hf/177Hf of Apollo 14 zircons versus absolute time (My) and time after the start of the solar system [calcium- and aluminum-rich inclusions (CAIs)] in millions of years.

    fig. S3. Hf model age variations depending on the 176Lu/177Hf ratios for the source.

    fig. S4. KREEP 176Lu/177Hf evolutions through decreasing melt percent, as given by pMELTS simulations.

    table S1A. U-Pb isotopic data (zircons also measured for Hf isotope composition and used for the determination of the age of the Moon).

    table S1B. U-Pb isotopic data (zircons not measured for Hf isotope composition).

    table S2. Tuning parameters of the coupled Cetac “Aridus II” and ThermoFinnigan Neptune MC-ICPMS.

    table S3A. Hf isotopic data and model age calculations for lunar zircons.

    table S3B. Summary of Hf isotopes measured on terrestrial standards.

    References (58, 59)

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. 176Hf/177Hf ratios normalized to the expected (present-day) value for standard zircons versus the magnitude of the peak stripping due to interfering Yb, measured as 173Yb+/177Hf +.
    • fig. S2. Initial 176Hf/177Hf of Apollo 14 zircons versus absolute time (My) and time after the start of the solar system calcium- and aluminum-rich inclusions (CAIs) in millions of years.
    • fig. S3. Hf model age variations depending on the 176Lu/177Hf ratios for the source.
    • fig. S4. KREEP 176Lu/177Hf evolutions through decreasing melt percent, as given by pMELTS simulations.
    • References (58, 59)

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    Other Supplementary Material for this manuscript includes the following:

    • table S1A (Microsoft Excel format). U-Pb isotopic data (zircons also measured for Hf isotope composition and used for the determination of the age of the Moon).
    • table S1B (Microsoft Excel format). U-Pb isotopic data (zircons not measured for Hf isotope composition).
    • table S2 (Microsoft Excel format). Tuning parameters of the coupled Cetac “Aridus II” and ThermoFinnigan Neptune MC-ICPMS.
    • table S3A (Microsoft Excel format). Hf isotopic data and model age calculations for lunar zircons.
    • table S3B (Microsoft Excel format). Summary of Hf isotopes measured on terrestrial standards.

    Files in this Data Supplement:

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