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Chondrule formation in particle-rich nebular regions at least hundreds of kilometres across

Nature volume 441, pages 483485 (25 May 2006) | Download Citation

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Abstract

Chondrules are millimetre-sized spherules (mostly silicate) that dominate the texture of primitive meteorites1. Their formation mechanism is debated, but their sheer abundance suggests that the mechanism was both energetic and ubiquitous in the early inner Solar System2. The processes suggested—such as shock waves, solar flares or nebula lightning3,4,5,6,7—operate on different length scales that have been hard to relate directly to chondrule properties. Chondrules are depleted in volatile elements, but surprisingly they show little evidence for the associated loss of lighter isotopes one would expect8. Here we report a model in which molten chondrules come to equilibrium with the gas that was evaporated from other chondrules, and which explains the observations in a natural way. The regions within which the chondrules formed must have been larger than 150–6,000 km in radius, and must have had a precursor number density of at least 10 m-3. These constraints probably exclude nebula lightning, and also make formation far from the nebula midplane problematic. The wide range of chondrule compositions may be the result of different combinations of the local concentrations of precursors and the local abundance of water ice or vapour.

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Acknowledgements

We thank E. Young for several discussions and A. Boss, L. Nittler, and F. Ciesla for comments which improved the manuscript. This work was supported by NASA's Planetary Geology and Geophysics, Origins of Solar Systems, and Cosmochemistry programmes.

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Affiliations

  1. Space Science Division, Ames Research Center, Moffett Field, California 94035, USA

    • Jeffrey N. Cuzzi
  2. Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington DC 20015, USA

    • Conel M. O'D. Alexander

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Competing interests

Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.

Corresponding author

Correspondence to Jeffrey N. Cuzzi.

Supplementary information

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  1. 1.

    Supplementary Notes

    This file contains Supplementary Discussion on: general relationships and assumptions; solving for local density where clouds from many chondrules overlap; diffusion of evaporated vapor in hydrogen gas; high pressures can preclude isotopic fractionation; details of chemical kinetic models; other meteoritic properties leading to similar chondrule number densities; and how are high chondrule concentrations produced?

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https://doi.org/10.1038/nature04834

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