Research ArticleGEOCHEMISTRY

Organic matter in extraterrestrial water-bearing salt crystals

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Science Advances  10 Jan 2018:
Vol. 4, no. 1, eaao3521
DOI: 10.1126/sciadv.aao3521
  • Fig. 1 Zag/Monahans meteorites and their halite crystals.

    (A) Diagram showing the lithologies of the Zag and Monahans meteorites, their dark (carbonaceous) clasts, the halite crystals, and the fluid and solid inclusions within the halite crystals. (B) Halite crystals hosted in the matrix regions of the Zag meteorite. The arrow marks one of the several halite crystals shown in this photo. (C) A microphotograph showing a halite crystal subsampled from the Zag meteorite. (D) Halite crystals subsampled from the Zag meteorite contained in a pre-sterilized glass ampoule before hot-water extraction.

  • Fig. 2 μ-L2MS spectra of the Zag halite.

    The y axis of the spectrum is normalized to the largest peak for the range shown, representing a 36-shot average of the μ-L2MS spectra. The chemical structures of the potential organic species are shown in orange (PAHs), blue (alkenes), and red (other lower-mass molecules). The low-mass organics are composed of derivatives and volatile species such as SO2 (64 amu) and 34SO2 (66 amu) and its fragment SO at a lower abundance (48 amu). The spectrum is dominated by low-mass C5–C10 hydrocarbons, such as alkenes (as shown by sequence of peaks separated by 14 amu), and PAHs/heterocycles, such as triazine (81 amu), chlorobenzene (112 amu), chloroaniline (127 amu), naphthalene (128 amu), acenaphthene (154 amu), and fluorene (166 amu). The potential assignments of N-bearing compounds such as triazine and chloroaniline account for the odd-mass peaks.

  • Fig. 3 Raman spectra and peak parameters of the halites and matrix in Zag and Monahans.

    (A) Representative Raman spectra (100 to 2300 cm−1 region) of the carbonaceous, halite-bearing clast (pink line) and halite grain (black line) of the Zag meteorite. The 100 to 300 cm−1 region of the plot has been expanded for clarity. Vertical lines mark the location of the typical Raman peaks of halite (135 and 204 cm−1), carbonate (around 1088 cm−1), and D and G bands (around 1373 and 1587 cm−1). (B) Raman G band spectral parameters of Zag matrix, Monahans halite residues, and carbonaceous chondrite–hosted MMC. Several residue grains were collected from the same grain of Monahans halite, and their Raman spectra parameters were expressed as individual points (yellow symbols). The black icons indicate a trend of MMC crystalline ordering in carbonaceous chondrites, from relatively poorly ordered CI chondrites to polycrystalline CV3 MMC. One grain of Monahans halite residue constitutes a single instance of MMC with affinity to CV3 chondrites (pink circle). Most MMC inclusions exhibit structural ordering similar to CI-CR-CM-CO chondrites (cyan circle), but one grain lies on a trendline between crystalline graphite and the main group. Thermal metamorphism does not drive ordering directly to graphite from disordered carbon, and spectra in this region are best explained as disordering of crystalline graphite, perhaps by shock. Overall, Monahans halite–hosted MMC is generally similar to CI-CR-CM-CO chondrites with minor input from CV3-like MMC and graphitic material that has been partially disordered. Error bars represent 1σ. arb. units, arbitrary units; FWHM, full width at half maximum.

  • Fig. 4 STXM-XANES of the residue from halite in Monahans.

    (A) STXM single energy image at 390 eV refracting atomic density. Black indicates areas of higher density. (B) Carbon map obtained by taking the −log(I289/I280) below (280 eV: I280) and on (289 eV: I289) the carbon K-edge. White indicates areas rich in carbon. (C) Spectral composed map. Red, organic area; green, inorganic area; and blue, blank (for example, holes). C-XANES spectra used to compose the red, green, and blue map are shown in fig. S3. (D) C-XANES spectrum of organic areas [red areas in (C)] on the FIB section. Peak #1: 285.0 eV, 1s-π* of aromatic C. Peak #2: 286.6 eV, 1s-π* of ketone (C=O). C-XANES of Monahans meteorite matrix is also shown as thin line for comparison. (E) N-XANES spectrum of organic areas [red areas in (C)]. Peak #3: 398.7 eV, 1s-π* of imine (C=N). Peak #4: 400.3 eV, 1s-π* of C=N in imidazole and/or protonated imine. N-XANES of Monahans meteorite matrix is also shown as a thin line for comparison. The peak assignments of C,N-XANES are based on previous studies (31, 66, 67).

  • Fig. 5 Isotopic compositions of the Monahans halite residue.

    (A) SE image. (B) NanoSIMS elemental image. Red, C; green, N; blue, O. Field of view = 10 μm2. The C-rich area (red) is well correlated with the organic area shown by STXM (red area in Fig. 4C). The green N-rich material appears to be a contaminant because it can also be found outside the FIB section. (C) H. (D) Isotope image of δD. (E) 12C. (F) 12C14N – N is detected as the molecular CN ion due to the lower yield of N compared to CN under the Cs+ beam. Isotope images of the C-rich region (G) δ13C and (H) δ15N. Scale bar, 3 μm. (I) O three-isotope diagram comparing the oxygen isotopic compositions of the halite residue to that of other solar system materials. YR, Young and Russell; CCAM, carbonaceous chondrite anhydrous mineral; TFL, terrestrial fractionation line.

  • Fig. 6 Relative amino acid abundances (total amino acid abundance = 1) of the 6 M HCl acid-hydrolyzed amino acid extract of the Zag matrix (Embedded Image), the non-hydrolyzed amino acid extract of the Zag matrix (Embedded Image), and the acid-hydrolyzed amino acid extract of the Zag halite (Embedded Image).

    Although the Zag matrix is γ-ABA–, β-ABA–, α-aminoisobutyric acid (α-AIB), and EACA-deficient, the halite is shown to exhibit an opposite trend and is enriched in these amino acids. The marked difference in the amino acid contents between the halite and matrix indicates their separate synthetic origins. The abbreviations of the amino acids are defined in table S1.

  • Table 1 Carbon, nitrogen, hydrogen, and oxygen isotopic compositions of the C-rich and N-rich area in the halite residues of the Monahans meteorite.

    Errors are reported as 1σ. Isotopic data of CI, CM, and CR chondrites and terrestrial organic matter are available in the studies of Alexander et al. (32) and Epstein et al. (68).

    Meteorite classSamplesIsotopic compositions (‰)
    δ13Cδ15NδDδ17Oδ18O
    H5Monahans halite residues
    C-rich area−37.6 ± 4.6+164.5 ± 14.4+42.5 ± 54.3+90.8 ± 37.1+18.1 ± 20.9
    N-rich area−56.1 ± 14.7+106.1 ± 14.7+50.5 ± 27.2+28.1 ± 11.8
    CIOrgueil−17.05 ± 0.04+30.7 ± 0.2+972 ± 2+14.5 ± 0.6
    CMMurchison−18.91 ± 0.01−1.0 ± 0.4+777 ± 27+13.2 ± 0.6
    CREET92042−22.19 ± 0.1+184.1 ± 1.4+3002 ± 12+14.2 ± 0.3
    CR (weathered)El Djou−23.18+44.5+223+12.5
    Terrestrial organic matter−60 to −25−10 to +20−350 to +50

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/1/eaao3521/DC1

    fig. S1. The 4- to 40-min region of the UPLC-FD chromatograms obtained for the OPA/NAC-labeled (15-min derivatization) 6 M HCl acid-hydrolyzed amino acid extract and the non-hydrolyzed amino acid extract of the Zag matrix, acid-hydrolyzed amino acid extract of the Zag halite, and the amino acid standard solution.

    fig. S2. An overview of the amino acid compositions of Zag matrix and halite compared to chondrites from different meteorite classes.

    fig. S3. C-XANES spectra used to compose the false color map in Fig. 4C.

    fig. S4. Representative UPLC-ToF-MS combined ion chromatograms of selected masses.

    fig. S5. Representative UPLC-ToF-MS ion chromatograms.

    table S1. Summary of the average blank-corrected amino acid abundances (in parts per billion by weight).

    table S2. Amino acid enantiomeric ratios (d/l) of the 6 M HCl acid-hydrolyzed amino acid extract (total) and the non-hydrolyzed amino acid extract (free) of the Zag matrix, acid-hydrolyzed amino acid extract of the Zag halite.

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. The 4- to 40-min region of the UPLC-FD chromatograms obtained for the OPA/NAC-labeled (15-min derivatization) 6 M HCl acid-hydrolyzed amino acid extract and the non-hydrolyzed amino acid extract of the Zag matrix, acid-hydrolyzed amino acid extract of the Zag halite, and the amino acid standard solution.
    • fig. S2. An overview of the amino acid compositions of Zag matrix and halite compared to chondrites from different meteorite classes.
    • fig. S3. C-XANES spectra used to compose the false color map in Fig. 4C.
    • fig. S4. Representative UPLC-ToF-MS combined ion chromatograms of selected masses.
    • fig. S5. Representative UPLC-ToF-MS ion chromatograms.
    • table S1. Summary of the average blank-corrected amino acid abundances (in parts per billion by weight).
    • table S2. Amino acid enantiomeric ratios (D/L) of the 6 M HCl acid-hydrolyzed amino acid extract (total) and the non-hydrolyzed amino acid extract (free) of the Zag matrix, acid-hydrolyzed amino acid extract of the Zag halite.

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