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Extreme oxygen isotope anomaly with a solar origin detected in meteoritic organics

Nature Geoscience volume 4, pages 165168 (2011) | Download Citation


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Materials formed in the early Solar System generally exhibit a characteristic oxygen isotopic signature known as the non-mass-dependent oxygen isotope anomaly1,2, the origins of which are unclear. The anomalies are thought to reflect isotopic fractionation in the chemical reaction that first formed solid material from the gaseous medium, but the proposed mechanism and environment of formation are the subject of debate3,4,5,6. Here we analyse micrometre-sized grains of acid-insoluble organic matter from a carbonaceous chondritic meteorite recovered in Antarctica. We find that the organic matter has the highest 18O/16O and 17O/16O ratios known in planetary material, except for pre-solar grains7. The oxygen ratios are enhanced by up to 53±11% and the 13C/12C values by 29±5% relative to terrestrial values. We suggest that the coherent enrichments of 17O, 18O and 13C in the organic matter can best be explained by its formation being due to the photodissociation of carbon monoxides in a gas medium at temperatures of about 60 K or higher. These conditions are equivalent to those expected at the envelope of the proto-solar nebula, and we suggest the organic matter formed there.

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Change history

  • 08 February 2011

    In the PDF version of this Letter originally published online, the year of publication should have been 2011. This error has now been corrected in all versions of the Letter.


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The meteorite sample for isotope studies on organic matter was provided to H.N. by the National Institute of Polar Research, Japan. We thank N. Sugiura for comments on the manuscript. K.H. and H.N. were supported in this study by JSPS and the Atmosphere and Ocean Research Institute, University of Tokyo.

Author information


  1. Department of Earth and Space Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan

    • Ko Hashizume
  2. Atmosphere and Ocean Research Institute, University of Tokyo, Kashiwa, Chiba 277-8564, Japan

    • Naoto Takahata
    •  & Yuji Sano
  3. Department of Earth and Planetary Sciences, Graduate School of Science, Kyushu University, Fukuoka 812-8581, Japan

    • Hiroshi Naraoka


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K.H. designed the study; H.N. prepared meteoritic and standard samples; K.H. and N.T. performed the SIMS measurements; K.H. prepared the manuscript; N.T., H.N. and Y.S. gave technical support and conceptual advice.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Ko Hashizume.

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