In the absence of a firm link between individual meteorites and their asteroidal parent bodies, asteroids are typically characterized only by their light reflection properties, and grouped accordingly into classes1,2,3. On 6 October 2008, a small asteroid was discovered with a flat reflectance spectrum in the 554–995 nm wavelength range, and designated 2008 TC3 (refs 4–6). It subsequently hit the Earth. Because it exploded at 37 km altitude, no macroscopic fragments were expected to survive. Here we report that a dedicated search along the approach trajectory recovered 47 meteorites, fragments of a single body named Almahata Sitta, with a total mass of 3.95 kg. Analysis of one of these meteorites shows it to be an achondrite, a polymict ureilite, anomalous in its class: ultra-fine-grained and porous, with large carbonaceous grains. The combined asteroid and meteorite reflectance spectra identify the asteroid as F class3, now firmly linked to dark carbon-rich anomalous ureilites, a material so fragile it was not previously represented in meteorite collections.
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We thank the University of Khartoum for support of the field campaigns, and students and staff of the Physics Department of the Faculty of Sciences for their efforts to recover the meteorites. P.J. is supported by the NASA Planetary Astronomy program. D.R. acknowledges the support of NASA's Cosmochemistry program (grant NNX07AI48G). A. Alunni, J. Travis-Garcia and L. Hofland of NASA Ames Research Center, and J. Herrin of NASA Johnson Space Flight Center, provided laboratory assistance. The work conducted at JPL/Caltech was under contract with NASA. The William Hershel Telescope is operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.
Author Contributions P.J., M.H.S., D.N., S.E. and A.M.K. led the field search for meteorites. M.E.Z., L.L. and G.A.R. performed the petrographic analysis. J.M.F. performed the trace element bulk chemistry analysis. D.R. performed the oxygen isotope analysis. A.S. performed the Raman analysis. S.R.C. calculated the orbit and ground track. A.F., S.D., H.H.H. and G.R. observed and analysed the astronomical spectrum. P.G.B. analysed the infrasound data. P.G.B., W.N.E. and P.J. performed dark-flight calculations. S.P.W., E.T., M.B.B. and R.E.S. facilitated and analysed the US Government satellite observations. R.D. and M.K. observed the asteroid light curve, which was analysed by P.P., J.B. and Z.C. analysed the Meteosat 8 observations. P.J. and J.V. investigated the link with possible other parent bodies. J.K. provided wind model data. J.A. and P.J. analysed train wind drift. J.L.B. and P.J. measured reflection spectra of the meteorite. R.L.M. and P.J. obtained optical imaging of the meteorite. S.A.S., S.N.M., M.N. and P.J. performed the mid-infrared analysis.
This file contains Supplementary Notes, Supplementary Figures S1-S2 with Legends, Supplementary Table S1 and Supplementary References
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Natural Hazards (2018)