The Fall of the Peekskill Meteorite: Video Observaüons, Atmospheric Path, Fragmentation Record and Orbit

A general overview of the events surrounding the fall of the Peekskill meteorite is presented. Earth, Moon, and Planets 68: 189-197, 1995. © 1995 Kluwer Academic Publlshers. Printed in the Netherlands. 190 1. Introduetion: The events surrounding the fall of the Peekskill meteorite on October 9th, 1992 are quite remarkable. Not only did the meteorite announce its arrival by hitting a parked car in suburban Peekskill, N.Y., but the fireball that preceded the fall of the meteorite was videographed by at least 16 independent videographers. Eye-witness accounts indicate that the fireball associated with the Peekskill meteodte first appeared over West Virginia at 23:48 UT (±1 min.). The fireball, which traveled in an approximately northeasterly direction, had a pronounced greenish colour, and attained an estimated peak visual magnitude of -13 (comparable to the Full Moon). During a luminous flight time that exceeded 40 seconds the fireball covered a ground path of some 700 to 800 km (Brown et al., 1994). The fireball's ground path and the meteorite recovery location are shown in figure 1. Figure 1. Ground path of the fireball, and the meteorite recovery site at Peekskill, New York. The ground track as actually recorded on video is represented by the solid line; the dotted line represents the undocumented trajectory past the last recorded video image; the thick dashed line is based upon eye-witness observations, while the thin dashed line represents the th¢oretical initial portion of the trajectory. 191 The meteorite recovered at Peekskill, New York (41" 17' N, 81" 55' W) had a mass of 12.4 kg, and was subsequently identified as an H6 rnonomict breccia meteorite (Wlotzka, 1994). The video record suggests (see section 2) that the Peekskill meteorite probably has several companions, however, given the fireball's shallow angle of trajectory (see seetion 4) the fall ellipse is large (Hughes, 1994). This fact coupled with the harsh terrain that exists in the Peekskill area would suggest that the recovery of related fragments is unlikely. 2. A t m o s p h e r i c f l ight gros s character i s t i c s : To date the authors have collected a total of 16 videographic tapes showing the fireballs passage through the Earth's atmosphere. It is our belief that more videos of the event do exist, and we continue out efforts to search these out. An analysis of the fireball's atmospheric flight has been made from four of the sixteen videos collected (Brown et al., 1994). The video stations are shown in figure 1, and are located at: Fairfax, Virginia; Johnstown, Pennsylvania; Pittsburgh, Pennsylvania; and Willoughby, Ohio. At the beginning of the video record the meteoroid's velocity and height were 14.7 km/s and 46.4 km respectively. At a height of --41.5 km extensive fragmentation of the main meteoroid body took place. Differential induced aerodynamicaly drag subsequently caused a significant, greater than 20 km, longitudinal displacement of the fragments. A transverse displacement amounting to ~1 km also developed in some of the smaller fragments (see figure 2). This latter displacement is presumably the result of either the interaction of individual bow shock waves, or to the fragments receiving an appreciable transverse velocity component at the tirne of their separation from a rotating parent body. KM has studied the deceleration of several distinctive fragments and finds characteristic dynamit masses of 100-300 kg. Furthermore, a dynamic mass of order 20-25 metric tons is inferred for the parent meteoroid. Radioisotope studies of the Peekskill meteorite (Graf et al., 1994) suggest that the parent meteoroid had an initial radius somewhere between 50 and