Steven D. Miller^a,*, William C. Straka III^b, A. Scott Bachmeier^b, Timothy J. Schmit^c, Philip T. Partain^a and Yoo-Jeong Noh^a

^aCooperative Institute for Research in the Atmosphere, Colorado State University, Fort Collins, CO 80523;
^bCooperative Institute for Meteorological Satellite Studies, University of Wisconsin–Madison, Madison, WI 53706; and
^cAdvanced Satellite Products Branch, Center for Satellite Applications and Research, National Oceanic and Atmospheric Administration, Madison, WI 53715

Large meteors (or superbolides [Ceplecha Z, et al. (1999) Meteoroids 1998:37–54]), although rare in recorded history, give sobering testimony to civilization’s inherent vulnerability. A not-so-subtle reminder came on the morning of February 15, 2013, when a large meteoroid hurtled into the Earth’s atmosphere, forming a superbolide near the city of Chelyabinsnk, Russia, ~1,500 km east of Moscow, Russia [Ivanova MA, et al. (2013) Abstracts of the 76th Annual Meeting of the Meteoritical Society, 5366]. The object exploded in the stratosphere, and the ensuing shock wave blasted the city of Chelyabinsk, damaging structures and injuring hundreds. Details of trajectory are important for determining its specific source, the likelihood of future events, and potential mitigation measures. Earth-viewing environmental satellites can assist in these assessments. Here we examine satellite observations of the Chelyabinsk superbolide debris trail, collected within minutes of its entry. Estimates of trajectory are derived from differential views of the significantly parallax-displaced [e.g., Hasler AF (1981) Bull Am Meteor Soc 52:194–212] debris trail. The 282.7 ± 2.3° azimuth of trajectory, 18.5 ± 3.8° slope to the horizontal, and 17.7 ± 0.5 km/s velocity derived from these satellites agree well with parameters inferred from the wealth of surface-based photographs and amateur videos. More importantly, the results demonstrate the general ability of Earth-viewing satellites to provide valuable insight on trajectory reconstruction in the more likely scenario of sparse or nonexistent surface observations.

Reference
Miller SD, Straka III WC, Bachmeier AS, Schmit TJ, Partain PT and Noh Y-J (2013) Earth-viewing satellite perspectives on the Chelyabinsk meteor event. PNAS 110:18092-18097.
[doi:10.1073/pnas.1307965110]

Link to Article

William M. Napier^a, Ted E. Bunch^b,*, James P. Kennett^c, James H. Wittke^b, Kenneth B. Tankersley^d, Gunther Kletetschka^e,f, George A. Howard^g, and Allen West^h

^aBuckingham Centre for Astrobiology, University of Buckingham, Buckingham MK18 1EG, United Kingdom;
^bGeology Program, School of Earth Science and Environmental Sustainability, Northern Arizona University, Flagstaff, AZ 86011;
^cDepartment of Earth Science and Marine Science Institute, University of California, Santa Barbara, CA 93106;
^dDepartments of Anthropology and Geology, University of Cincinnati, Cincinnati, OH 45221;
^eFaculty of Science, Charles University in Prague, 128 43 Prague, Czech Republic;
^fInstitute of Geology, Academy of Sciences of the Czech Republic, Public Research Institute, 165 00 Prague, Czech Republic;
^gRestoration Systems, LLC, Raleigh, NC 27604; and
^hGeoScience Consulting, Dewey, AZ 86327

This is a reply to the PNAS comment of Boslough et al. (2013).

Reference
Napier WM, Bunch TE, Kennett JP, Wittke JH, Tankersley KB, Kletetschka G, Howard GA and West A (2013) Reply to Boslough et al.: Decades of comet research counter their claims. PNAS 110:E4171. Reply to Comment
[doi:10.1073/pnas.1315467110]

Link to Article

Mark Boslough^a,*, Alan W. Harris^b, Clark Chapman^c, and David Morrison^d

^aSandia National Laboratories, Albuquerque, NM 87185;
^bMoreData!, La Cañada, CA 91011;
^cSouthwest Research Institute, Boulder, CO 80302; and
^dSETI Institute, Mountain View, CA 94043

This is a comment to the PNAS article of Wittke et al. (2013).

Reference
Boslough M, Harris AW, Chapman C and Morrison D (2013) Younger Dryas impact model confuses comet facts, defies airburst physics. PNAS 110:E4170. Comment
[doi:10.1073/pnas.1313495110]

Link to Article