Trajectory and orbit of the Tunguska meteorite revisited

Abstract

Abstract-A critical survey is presented of all determinations of the azimuth and inclination of the Tunguska meteorite's trajectory based either on eyewitness testimonies or on the mathematical treatment of the forestleveling field in the area of the catastrophe. The eyewitness testimonies collected in the neighborhood of the Nizhnyaya Tunguska River indicate the most probable azimuth of the trajectory projection to be 104' from the north to the east, which is close to the most recent azimuth estimate from the forest-leveling field, 99". For the most part of the trajectory, its inclination could not exceed 15". However, it is seen from aerodynamic calculations that the combined action of the gravity field and a nonzero aerodynamic lift could increase the inclination to 40" as the end of the trajectory was approached. Meteoroid orbits are calculated for a broad family of trajectories with azimuths ranging from 99' (Fast et al., 1976) to 137 ' (Krinov, 1949) and geocentric velocities ranging from 25 to 40 km/s. Orbits with large azimuth values ( 120" and larger) are shown to belong to the asteroidal type. They are succeeded by the orbits of short-period and long-period comets, whereas very small azimuth values and large geocentric velocities correspond to the region of hyperbolic orbits. Certain restrictions on the possible trajectory azimuths and geocentric velocities of the Tunguska body are imposed by this study.

Probable asteroidal origin of the Tunguska Cosmic Body

“…On the other hand, Bronshten (1999a) performed a similar investigation on data from eyewitnesses and from forest devastation. He too obtained a small set of orbits consistent with the cometary hypothesis, while all radiants for geocentric speed smaller than 30 km s −1 correspond to Apollo-like asteroids.…”

The nature of the Tunguska meteorite

“…(6) The idea that the Tunguska body was the nucleus or a splinter of a comet is confirmed by the orbital elements deduced from the most probable trajectory-projection azimuth of this body (Bronshten, 1999).…”

“…Recently, it was used in a somewhat modified form by Bronshten (1 999), who constructed the diagram: (trajectory azimuthHentry velocity) and showed what combinations of these parameters lead to orbits typical of particular classes of bodies (asteroids, short-period comets, and long-period comets) and to hyperbolic orbits. For the most probable trajectory azimuth, 104' (Zotkin, 1972;Bronshten, 1999), cometary orbits correspond to geocentric velocities v , > 27 km/s, whereas for an azimuth of llOo, preferred by Sekanina, the bounding velocity will be 29 k d s . The value a1 = 3 AU is chosen here as a conventional boundary.…”

“…In addition to the azimuth, the inclination of the trajectory to the horizon appreciably affects the orbital elements. For instance, the results presented in Table 1 were obtained for the azimuth A0 = 104' (Bronshten, 1999).…”

Commission 22: Meteors, Meteorites and Interplanetary Dust: (Meteores, Meteorites Et Poussiere Interplanetaire)

“…Data on the trajectory and orbit of a superbolide over Greenland on December 9, 1997 are presented in Pedersen et al (2001). The trajectory and orbit of the Tunguska event are discussed in Bronshten (1999). The theory of penetration of large meteoric bodies into the atmosphere is described in Nemchinov, Popova k Teterev (1999).…”