presented to the

International Conference Asteroids, Comets, Meteors, July 1999


M. Di Martino (Torino Astronomical Observatory, Italy), P. Farinella (University of Trieste, Italy), G. Longo (University of Bologna, Italy)

          The Physics Department of Bologna University, together with researchers of the Torino Astronomical Observatory and of the CNR Institute of Marine Geology (Bologna), is organising a two weeks scientific expedition to Tunguska (Central Siberia). About 25 persons will participate to the expedition planned for the second half of July 1999. The expedition will carry out a systematic exploration of the site of the so-called Tunguska event (June 30, 1908). The fundamental tasks of the expedition are: (1) the study of Ceko lacustrine sediments, (2) radar and photographic observations, (3) the search for cosmic body fragments which could have fallen before the explosion "epicentre", (4) the measurement of environmental radiation. The lake Ceko, 8 km away from the explosion epicentre, has been chosen to search for sedimentary microparticles coming from the disintegration of the cosmic body. The lake topography will be obtained by a satellite system (GPS) and a bathymetric profile net will be constructed by a digital ecograph. By using a "sub bottom penetration system", a stratigraphic map of the bottom will be obtained to choose the sites where the samples will be collected. At the same time, a "side scan sonar" will take ultrasound photographs of the lake bottom. Then, an accurate inspection of the lake bottom will be carried out by a remotely controlled underwater telecamera. Undisturbed samples will be collected by using a "box corer" and a sampling will be performed by using a gravity corer. The samples will be later analysed in laboratory. A topographic survey of the area, performed using a GPS system, will be used to re-examine the aerophotographic material, obtained in 1938 under the direction of L.A. Kulik. The comparison between the 1938 pictures and the new survey should give further information on the direction of the trees felled by the explosion. The preliminary results of the expedition will be presented in the proceeding of this conference.

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