A cometary building block in a primitive asteroidal meteorite


Meteorites originating from primitive C-type asteroids are composed of materials from the Sun’s protoplanetary disk, including up to a few per cent organic carbon. In contrast, some interplanetary dust particles and micrometeorites have much higher carbon contents, up to >90%, and are thought to originate from icy outer Solar System bodies and comets. Here we report an approximately 100-µm-diameter very carbon-rich clast, with highly primitive characteristics, in the matrix of a CR2 chondrite, LaPaz Icefield 02342. The clast may represent a cometary building block, largely unsampled in meteorite collections, that was captured by a C-type asteroid during the early stages of planet formation. The existence of this cometary microxenolith supports the idea of a radially inward transport of materials from the outer protoplanetary disk into the CR chondrite reservoir during the formation of planetesimals. Moreover, the H-isotopic composition of the clast is suggestive of a temporal evolution of organic isotopic compositions in the comet-forming region of the disk.

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Fig. 1: CRC in section of LAP 02342 meteorite.
Fig. 2: O-rich presolar grains in LAP 02342.
Fig. 3: 16O-poor material in the CRC.
Fig. 4: OM in CRC.
Fig. 5: FIB sections from LAP 02342.
Fig. 6: STEM data for CRC FIB section.
Fig. 7: STEM data for 16O-poor CRC FIB section.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.


  1. 1.

    Kruijer, T. S., Burkhardt, C., Budde, G. & Kleine, T. Age of Jupiter inferred from the distinct genetics and formation times of meteorites. Proc. Natl Acad. Sci. USA 114, 6712–6716 (2017).

    ADS  Google Scholar 

  2. 2.

    Weisberg, M. K., Prinz, M., Clayton, R. N. & Mayeda, T. K. The CR (Renazzo-type) carbonaceous chondrite group and its implications. Geochim. Cosmochim. Acta 57, 1567–1586 (1993).

    ADS  Article  Google Scholar 

  3. 3.

    Alexander, C. M.O’D., Fogel, M., Yabuta, H. & Cody, G. D. The origin and evolution of chondrites recorded in the elemental and isotopic compositions of their macromolecular organic matter. Geochim. Cosmochim. Acta 71, 4380–4403 (2007).

    ADS  Article  Google Scholar 

  4. 4.

    Nguyen, A. N., Nittler, L. R., Stadermann, F. J., Stroud, R. M. & Alexander, C. M. O’D. Coordinated analyses of presolar grains in the Allan Hills 77307 and Queen Elizabeth Range 99177 meteorites. Astrophys. J 719, 166–189 (2010).

    ADS  Article  Google Scholar 

  5. 5.

    Van Kooten, E. M. M. E. et al. Isotopic evidence for primordial molecular cloud material in metal-rich carbonaceous chondrites. Proc. Natl Acad. Sci. USA 113, 2011–2016 (2016).

    ADS  Article  Google Scholar 

  6. 6.

    Howard, K. T., Alexander, C. M. O’D., Schrader, D. L. & Dyl, K. A. Classification of hydrous meteorites (CR, CM and C2 ungrouped) by phyllosilicate fraction: PSD-XRD modal mineralogy and planetesimal environments. Geochim. Cosmochim. Acta 149, 206–222 (2015).

    ADS  Article  Google Scholar 

  7. 7.

    Schramm, L. S., Brownlee, D. E. & Wheelock, M. M. Major element composition of stratospheric micrometeorites. Meteoritics 24, 99–112 (1989).

    ADS  Article  Google Scholar 

  8. 8.

    Thomas, K. L., Blanford, G. E., Keller, L. P., Klock, W. & McKay, D. S. Carbon abundance and silicate mineralogy of anhydrous interplanetary dust particles. Geochim. Cosmochim. Acta 57, 1551–1566 (1993).

    ADS  Article  Google Scholar 

  9. 9.

    Duprat, J. et al. Extreme deuterium excesses in ultracarbonaceous micrometeorites from central Antarctic snow. Science 328, 742–745 (2010).

    ADS  Article  Google Scholar 

  10. 10.

    Dartois, E. et al. UltraCarbonaceous Antarctic micrometeorites, probing the Solar System beyond the nitrogen snow-line. Icarus 224, 243–252 (2013).

    ADS  Article  Google Scholar 

  11. 11.

    Dartois, E. et al. Dome C ultracarbonaceous Antarctic micrometeorites: infrared and Raman fingerprints. Astron. Astrophys. 609, A65 (2018).

    Article  Google Scholar 

  12. 12.

    Trigo-Rodríguez, J. M. et al. Evidence for extended aqueous alteration in CR carbonaceous chondrites. Lunar Planet. Sci. 44, abstr. 1929 (2013).

    ADS  Google Scholar 

  13. 13.

    Wasson, J. T. & Rubin, A. E. Composition of matrix in the CR chondrite LAP 02342. Geochim. Cosmochim. Acta 73, 1436–1460 (2009).

    ADS  Article  Google Scholar 

  14. 14.

    Trigo-Rodriguez, J. M. & Blum, J. Tensile strength as an indicator of the degree of primitiveness of undifferentiated bodies. Planet. Space Sci. 57, 243–249 (2009).

    ADS  Article  Google Scholar 

  15. 15.

    Nittler, L. R. et al. High abundances of presolar grains and 15N-rich organic matter in CO3.0 chondrite dominion range 08006. Geochim. Cosmochim. Acta 226, 107–131 (2018).

    ADS  Article  Google Scholar 

  16. 16.

    Floss, C. & Haenecour, P. Presolar silicate grains: abundances, isotopic and elemental compositions, and the effects of secondary processing. Geochem. J. 50, 3–25 (2016).

    ADS  Article  Google Scholar 

  17. 17.

    Davidson, J. et al. Abundances of presolar silicon carbide grains in primitive meteorites determined by NanoSIMS. Geochim. Cosmochim. Acta 139, 248–266 (2014).

    ADS  Article  Google Scholar 

  18. 18.

    Sakamoto, N. et al. Remnants of the early Solar System water enriched in heavy oxygen isotopes. Science 317, 231–233 (2007).

    ADS  Article  Google Scholar 

  19. 19.

    Starkey, N. A., Franchi, I. A. & Lee, M. R. Isotopic diversity in interplanetary dust particles and preservation of extreme 16O-depletion. Geochim. Cosmochim. Acta 142, 115–131 (2014).

    ADS  Article  Google Scholar 

  20. 20.

    Busemann, H. et al. Interstellar chemistry recorded in organic matter from primitive meteorites. Science 312, 727–730 (2006).

    ADS  Article  Google Scholar 

  21. 21.

    Urquhart, S. G. & Ade, H. Trends in the carbonyl core (C 1s, O 1s) → π*C=O transition in the near-edge X-ray absorption fine structure spectra of organic molecules. J. Phys. Chem. B 106, 8531–8538 (2002).

    Article  Google Scholar 

  22. 22.

    Alexander, C. M. O’D., Cody, G. D., Gregorio, B. T. D., Nittler, L. R. & Stroud, R. M. The nature, origin and modification of insoluble organic matter in chondrites, the major source of Earth’s C and N. Chem. Erde 77, 227–256 (2017).

    Article  Google Scholar 

  23. 23.

    Keller, L. P. & Messenger, S. On the origins of GEMS grains. Geochim. Cosmochim. Acta 75, 5336–5365 (2011).

    ADS  Article  Google Scholar 

  24. 24.

    Le Guillou, C., Changela, H. G. & Brearley, A. J. Widespread oxidized and hydrated amorphous silicates in CR chondrites matrices: implications for alteration conditions and H2 degassing of asteroids. Earth Planet. Sci. Lett. 420, 162–173 (2015).

    ADS  Article  Google Scholar 

  25. 25.

    Abreu, N. M. Why is it so difficult to classify Renazzo-type (CR) carbonaceous chondrites? Implications from TEM observations of matrices for the sequences of aqueous alteration. Geochim. Cosmochim. Acta 194, 91–122 (2016).

    ADS  Article  Google Scholar 

  26. 26.

    Bradley, J. P. et al. An infrared spectral match between GEMS and interstellar grains. Science 285, 1716–1718 (1999).

    ADS  Article  Google Scholar 

  27. 27.

    Yabuta, H. et al. Formation of an ultracarbonaceous Antarctic micrometeorite through minimal aqueous alteration in a small porous icy body. Geochim. Cosmochim. Acta 214, 172–190 (2017).

    ADS  Article  Google Scholar 

  28. 28.

    Nakamura-Messenger, K., Clemett, S. J., Messenger, S. & Keller, L. P. Experimental aqueous alteration of cometary dust. Meteorit. Planet. Sci. 46, 843–856 (2011).

    ADS  Article  Google Scholar 

  29. 29.

    Leroux, H., Cuvillier, P., Zanda, B. & Hewins, R. H. GEMS-like material in the matrix of the Paris meteorite and the early stages of alteration of CM chondrites. Geochim. Cosmochim. Acta 170, 247–265 (2015).

    ADS  Article  Google Scholar 

  30. 30.

    Alexander, C. M. O’D. et al. The provenances of asteroids, and their contributions to the volatile inventories of the terrestrial planets. Science 337, 721–723 (2012).

    ADS  Article  Google Scholar 

  31. 31.

    Matrajt, G., Messenger, S., Brownlee, D. & Joswiak, D. Diverse forms of primordial organic matter identified in interplanetary dust particles. Meteorit. Planet. Sci. 47, 525–549 (2012).

    ADS  Article  Google Scholar 

  32. 32.

    Floss, C., Noguchi, T. & Yada, T. Hydrogen and nitrogen imaging of Ultra-Carbonaceous Antarctic Micrometeorite TT54B397. Meteorit. Planet. Sci. Suppl. 76, 5230 (2013).

  33. 33.

    Trigo-Rodríguez, J. M. & Llorca, J. On the sodium overabundance in cometary meteoroids. Adv. Space Res. 39, 517–525 (2007).

    ADS  Article  Google Scholar 

  34. 34.

    Trigo-Rodríguez, J. M., Llorca, J. & Fabregat, J. Chemical abundances determined from meteor spectra—II. Evidence for enlarged sodium abundances in meteoroids. Mon. Not. R. Astron. Soc. 348, 802–810 (2004).

    ADS  Article  Google Scholar 

  35. 35.

    McKeegan, K. D. et al. The oxygen isotopic composition of the Sun inferred from captured solar wind. Science 332, 1528–1532 (2011).

    ADS  Article  Google Scholar 

  36. 36.

    Lyons, J. R. & Young, E. D. CO self-shielding as the origin of oxygen isotope anomalies in the early solar nebula. Nature 435, 317–320 (2005).

    ADS  Article  Google Scholar 

  37. 37.

    Yurimoto, H. & Kuramoto, K. Molecular cloud origin for the oxygen isotope heterogeneity in the Solar System. Science 305, 1763–1766 (2004).

    ADS  Article  Google Scholar 

  38. 38.

    Labidi, J., Farquhar, J., Alexander, C. M. O’D., Eldridge, D. L. & Oduro, H. Mass independent sulfur isotope signatures in CMs: implications for sulfur chemistry in the early Solar System. Geochim. Cosmochim. Acta 196, 326–350 (2017).

    ADS  Article  Google Scholar 

  39. 39.

    Bharmoria, P., Gehlot, P. S., Gupta, H. & Kumar, A. Temperature-dependent solubility transition of Na2SO4 in water and the effect of NaCl therein: solution structures and salt water dynamics. J. Phys. Chem. B 118, 12734–12742 (2014).

    Article  Google Scholar 

  40. 40.

    Alexander, C. M. O’D., Bowden, R., Fogel, M. L. & Howard, K. T. Carbonate abundances and isotopic compositions in chondrites. Meteorit. Planet. Sci. 50, 810–833 (2015).

    ADS  Article  Google Scholar 

  41. 41.

    Jilly-Rehak, C. E., Huss, G. R., Nagashima, K. & Schrader, D. L. Low-temperature aqueous alteration on the CR chondrite parent body: implications from in situ oxygen-isotope analyses. Geochim. Cosmochim. Acta 222, 230–252 (2018).

    ADS  Article  Google Scholar 

  42. 42.

    Augé, B. et al. Irradiation of nitrogen-rich ices by swift heavy ions: clues for the formation of ultracarbonaceous micrometeorites. Astron. Astrophys. 592, A99 (2016).

    Article  Google Scholar 

  43. 43.

    Ciesla, F. J. & Sandford, S. A. Organic synthesis via irradiation and warming of ice grains in the solar nebula. Science 336, 452–454 (2012).

    ADS  Article  Google Scholar 

  44. 44.

    Sugiura, N. & Fujiya, W. Correlated accretion ages and ɛ54Cr of meteorite parent bodies and the evolution of the solar nebula. Meteorit. Planet. Sci. 49, 772–787 (2014).

    ADS  Article  Google Scholar 

  45. 45.

    Brownlee, D. et al. Comet 81P/Wild 2 under a microscope. Science 314, 1711–1716 (2006).

    ADS  Article  Google Scholar 

  46. 46.

    Schrader, D. L. et al. The retention of dust in protoplanetary disks: evidence from agglomeratic olivine chondrules from the outer Solar System. Geochim. Cosmochim. Acta 223, 405–421 (2018).

    ADS  Article  Google Scholar 

  47. 47.

    Briani, G., Morbidelli, A., Gounelle, M. & Nesvorný, D. Evidence for an asteroid–comet continuum from simulations of carbonaceous microxenolith dynamical evolution. Meteorit. Planet. Sci. 46, 1863–1877 (2011).

    ADS  Article  Google Scholar 

  48. 48.

    Slodzian, G., Hillion, F., Stadermann, F. J. & Zinner, E. QSA influences on isotopic ratio measurements. Appl. Surf. Sci. 231–232, 874–877 (2004).

    ADS  Article  Google Scholar 

  49. 49.

    Nittler, L. R., Alexander, C. M. O’D., Gao, X., Walker, R. M. & Zinner, E. Stellar sapphires: the properties and origins of presolar Al2O3 in meteorites. Astrophys. J. 483, 475–495 (1997).

    ADS  Article  Google Scholar 

  50. 50.

    Hoppe, P., Leitner, J. & Kodolányi, J. The stardust abundance in the local interstellar cloud at the birth of the Solar System. Nat. Astron. 1, 617–620 (2017).

    ADS  Article  Google Scholar 

  51. 51.

    Bassim, N. D. et al. Minimizing damage during FIB sample preparation of soft materials. J. Microsc. 245, 288–301 (2012).

    Article  Google Scholar 

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J.M.T.-R. and C.E.M.-C. acknowledge funding support from Spanish grants AYA 2011-26522 and AYA 2015-67175-P. C.E.M.-C. and S.T. participated in this study in the frame of a PhD in Physics at the Autonomous University of Barcelona. L.R.N., C.M.O’D.A., R.M.S. and B.T.D. acknowledge funding support from NASA grants NNX10AI63G and NNH16AC42I. This research used resources of the Advanced Light Source, which is a DOE Office of Science User Facility under contract no. DE-AC02-05CH11231. We thank H. Yabuta and J. Duprat for helpful comments that improved this paper.

Author information




J.M.T.-R. and C.E.M.-C. identified the C-rich clast and brought it to the attention of the other authors. J.M.T.-R., L.R.N. and R.M.S. designed the study. All authors participated in data acquisition and analysis. L.R.N. and J.M.T.-R. wrote the paper with substantial input from other authors.

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Correspondence to Larry R. Nittler.

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Journal peer review information: Nature Astronomy thanks Jean Duprat, Hikaru Yabuta and the other anonymous reviewers for their contribution to the peer review of this work.

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Nittler, L.R., Stroud, R.M., Trigo-Rodríguez, J.M. et al. A cometary building block in a primitive asteroidal meteorite. Nat Astron 3, 659–666 (2019). https://doi.org/10.1038/s41550-019-0737-8

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