Fall, classification, and exposure history of the Mifflin L5 chondrite
Article first published online: 4 MAR 2013
© The Meteoritical Society, 2013.
Meteoritics & Planetary Science
Volume 48, Issue 4, pages 641–655, April 2013
How to Cite
Kita, N. T., Welten, K. C., Valley, J. W., Spicuzza, M. J., Nakashima, D., Tenner, T. J., Ushikubo, T., MacPherson, G. J., Welzenbach, L., Heck, P. R., Davis, A. M., Meier, M. M. M., Wieler, R., Caffee, M. W., Laubenstein, M. and Nishiizumi, K. (2013), Fall, classification, and exposure history of the Mifflin L5 chondrite. Meteoritics & Planetary Science, 48: 641–655. doi: 10.1111/maps.12077
- Issue published online: 12 APR 2013
- Article first published online: 4 MAR 2013
- Manuscript Accepted: 4 JAN 2013
- Manuscript Received: 7 FEB 2012
- NASA. Grant Numbers: NNX10AH77G, NNX08AY83G, NNX11AC69G, NNX09AG39G
- Swiss National Science Foundation
The Mifflin meteorite fell on the night of April 14, 2010, in southwestern Wisconsin. A bright fireball was observed throughout a wide area of the midwestern United States. The petrography, mineral compositions, and oxygen isotope ratios indicate that the meteorite is a L5 chondrite fragmental breccia with light/dark structure. The meteorite shows a low shock stage of S2, although some shock-melted veins are present. The U,Th-He age is 0.7 Ga, and the K-Ar age is 1.8 Ga, indicating that Mifflin might have been heated at the time of the 470 Ma L-chondrite parent body breakup and that U, Th-He, and K-Ar ages were partially reset. The cosmogenic radionuclide data indicate that Mifflin was exposed to cosmic rays while its radius was 30–65 cm. Assuming this exposure geometry, a cosmic-ray exposure age of 25 ± 3 Ma is calculated from cosmogenic noble gas concentrations. The low 22Ne/21Ne ratio may, however, indicate a two-stage exposure with a longer first-stage exposure at high shielding. Mifflin is unusual in having a low radiogenic gas content combined with a low shock stage and no evidence of late stage annealing; this inconsistency remains unexplained.