International Conference Asteroids, Comets, Meteors, July 1999
25.25-P: SEARCH FOR COSMIC MATTER IN A TUNGUSKA LAKE
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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