THE TUNGUSKA METEORITE PROBLEM TODAY

This paper contains basic data relating to the Tunguska Meteorite (TM) as late as 1996, including flight and explosion of a giant bolide in Siberia on 30 June 1908, related geophysical effects, the results of s earch of the TM matter and the environmental after effects of the even t. The TNT equivalent of the Tunguska explosion is estimated between 1 0 and 40 megatons (most probably 15 megatons), probable energy 4.2 x 1 0(23)-1.7 x 10(24) erg, altitude of the explosion 5-10 km. The explosi on devastated a 2150+/-25 km(2) forest area and produced a radiant bur n of flora at more than 100 km(2). The problem of optical events in th e summer of 1908 connected to the Tunguska explosion is discussed, as well as that of the origin of element and isotropic anomalies in the a rea, the most striking feature being peculiarities in the C, H and Pb isotopic composition. A critical analysis is given of hypotheses propo sed to explain TM problem. The hypotheses proceeding from concepts of the TM low and hyperlow (<0.01 g/cm(3)) density are shown to be incons istent. It is stated that nowadays the basic aspect of the TM nature d iscussion is an alternative ''stony asteroid-comet''. Though the final choice between them has not yet been made, the chances of the stony a steroid version have recently grown substantially. The first priority is to solve a set of questions in order that further development of th is problem can be defined as follows: (1) the fate of the meteorite fr agments in case the TM was really a stony asteroid; (2) the possibilit y of a carbonaceous chondrite and mellow comet nucleus penetration int o the troposphere; (3) the nature of the element and isotopic cosmoche mical anomaly in the area of the Tunguska explosion epicentre; (4) the mechanism of geomagnetic effect and optical anomalies developed in th e summer of 1908; (5) the possibility of a quick (within hours) transf er of dusty matter from the area of the Tunguska event to Central Asia , European Russia and Western Europe by stratospheric and mesospheric winds and (6) the cause of the mutation process in the area of the Tun guska catastrophe. All these questions might be solved much faster wit hin the frames of international scientific cooperation as recently out lined and of continued fieldwork in the area of the Tunguska explosion . In this way the necessary conditions will be created to build up a s ynthetic theory of the Tunguska event, in order to explain not only th e explosion of a space object at the Podkamennaya Tunguska, but the en tire complex of anomalous cosmophysical events in the summer of 1908. (C) 1998 Elsevier Science Ltd. All rights reserved.