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Day et al. reply

Nature volume 459, page E2 (28 May 2009) | Download Citation



Replying to: R. Arculus, I. H. Campbell, S. M. McLennan & S. R. Taylor Nature 459 10.1038/nature08077 (2009)

Arculus et al.1 raise an important question regarding the use of terrestrial rock nomenclature to characterize extraterrestrial materials. Here the issue relates to the definition of ‘andesite’, and whether the felsic achondrite meteorites GRA 06128 and GRA 06129 (GRA 06128/9) can and should be classified using this term2. More broadly, the question is whether extraterrestrial rocks should be classified using standard petrologic and geochemical criteria, such as mineralogy and major-element bulk composition, developed for the description of terrestrial rocks3,4. The approach of Arculus et al.1 is that petrogenetic process is of equal or greater importance when classifying a rock. This question must ultimately be decided by the scientific community.

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    , , & Asteroids and andesites. Nature 459, 10.1038/nature08077 (2009).

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    et al. Early formation of evolved asteroidal crust. Nature 457, 179–182 (2009)

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    A Classification of Igneous Rocks and Glossary of Terms: Recommendations of the International Union of Geological Sciences Subcommission on the Systematics of Igneous Rocks (Blackwell Scientific, 1989)

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    & The IUGS systematics of igneous rocks. J. Geol. Soc. Lond. 148, 825–833 (1991)

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    , , & (eds) New Views of the Moon (Reviews in Mineralogy and Geochemistry, Vol. 60, Mineralogical Society of America, 2006)

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    , & Granite: a planetary point of view. Gondwana Res. 5, 261–273 (2002)

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    & No water, no granites — no oceans, no continents. Geophys. Res. Lett. 10, 1061–1064 (1983)

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Author information


  1. *Department of Geology, University of Maryland, College Park, Maryland 20742, USA.

    • J. M. D. Day
    • , R. D. Ash
    • , J. J. Bellucci
    • , W. F. McDonough
    •  & R. J. Walker
  2. †Department of Earth and Planetary Sciences, Planetary Geosciences Institute, University of Tennessee, Knoxville, Tennessee 37996, USA

    • Y. Liu
    •  & L. A. Taylor
  3. ‡Geophysical Laboratory, Carnegie Institution of Washington, Washington DC 20015, USA

    • D. Rumble III


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