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Effect of a synchrotron X‐ray microtomography imaging experiment on the amino acid content of a CM chondrite
Author(s) -
Friedrich Jon M.,
Glavin Daniel P.,
Rivers Mark L.,
Dworkin Jason P.
Publication year - 2016
Publication title -
meteoritics and planetary science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.09
H-Index - 100
eISSN - 1945-5100
pISSN - 1086-9379
DOI - 10.1111/maps.12595
Subject(s) - murchison meteorite , chondrite , carbonaceous chondrite , chemistry , synchrotron , meteorite , x ray , synchrotron radiation , analytical chemistry (journal) , materials science , radiochemistry , physics , optics , astrobiology , chromatography
X‐ray microcomputed tomography and synchrotron X‐ray microcomputed tomography (μ CT ) are becoming popular tools for the reconnaissance imaging of chondrites. However, there are occasional concerns that the use of μ CT may be detrimental to organic components of a chondrite. Soluble organic compounds represent ~2–10% of the total solvent extractable carbon in CI and CM carbonaceous chondrites and amino acids are among the most abundant compounds in the soluble organic fraction. We irradiated two samples of the Murchison CM 2 carbonaceous chondrite under conditions slightly harsher (increased beam exposure time) than those typically used for x‐ray μ CT imaging experiments to determine if detectable changes in the amino acid abundance and distribution relative to a nonexposed control sample occurred. After subjecting two meteorite portions to ionizing radiation dosages of 1.1 kiloGray ( kG y) and 1.2 kGy with 48.6 and 46.6 keV monochromatic X‐rays, respectively, we analyzed the amino acid content of each sample. Within analytical errors, we found no differences in the amino acid abundances or enantiomeric ratios when comparing the control samples (nonexposed Murchison) and the irradiated samples. We show with calculations that any sample heating due to x‐ray exposure is negligible. We conclude that a monochromatic synchrotron X‐ray μ CT experiment at beamline 13‐ BM ‐D of the Advanced Photon Source, which imparts ~1 kG y doses, has no detectable effect on the amino acid content of a carbonaceous chondrite. These results are important for the initial reconnaissance of returned samples from the OSIRIS ‐ RE x and Hayabusa 2 asteroid sample return missions.