Exposure history of the Peekskill (H6) meteorite

Th Graf, K. Marti, S. Xue, G. F. Herzog, J. Klein, R. Middleton, K. Metzler, R. Herd, P. Brown, J. F. Wacker, A. J.T. Jull, J. Masarik, V. T. Koslowsky, H. R. Andrews, R. J.J. Cornett, W. G. Davies, B. F. Greiner, Y. Imahori, J. W. Mckay, G. M. MiltonJ. C.D. Milton

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


The Peekskill H6 meteorite fell on 1992 October 9. We report extensive measurements of cosmic-ray produced stable nuclides of He, Ne, and Ar, of the radionuclides 22Na, 60Co, 14C, 36Cl, 26Al, and 10Be, and of cosmic-ray track densities. After correction for shielding via the 22Ne/21Ne ratio, the concentrations of cosmic-ray produced 3He, 21Ne and 38Ar give an average exposure age of 25 Ma, which is considered to be a lower limit on the true value. The 10Be/21Ne age is 32 Ma and falls onto a peak in the H-chondrite exposure age distribution. The activities of 26Al, 14C, 36Cl, and 10Be are all close to the maximum values expected for H-chondrites. Together with cosmic-ray track densities and the 22Ne/21Ne ratio, these radionuclide data place the samples at a depth >20 cm in a meteoroid with a radius >40 cm. In contrast, the 60Co activity requires a near-surface location and/or a much smaller body. Calculations show that a flattened geometry for the Peekskill meteoroid does not explain the observations in the context of a one-stage irradiation. A two-stage model can account for the data. We estimate an upper bound of 70 cm on the radius of the earlier stage of irradiation and conclude that Peekskill's radius was <70 cm when it entered the Earth's atmosphere. This size limit is somewhat smaller than the dynamic determinations (Brown et al., 1994).

Original languageEnglish (US)
Pages (from-to)25-30
Number of pages6
JournalMeteoritics and Planetary Science
Issue number1
StatePublished - Jan 1997

ASJC Scopus subject areas

  • Geophysics
  • Space and Planetary Science


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