Traces Of The Vitim Meteoroid

In 2002-2003, three expeditions involving specialists of the Institutes of Geochemistry, of Solar-Terrestrial Geophysics, and of the Earth’s Crust, Siberian Branch, Russian Academy of Sciences (Irkutsk) looked for traces of meteoroid that had fallen down in the north-east of the Irkutsk Province, in the Mamsko-Chuisk region. None of the expeditions found either craters or meteoroid fragments. Only fallen trees and minor particles of meteorite substance mark the direction of celestial body falling.

At night of September 25, 2002, inhabitants of the Mamsko-Chuisk and Bodaibinsk regions (Irkutsk Province) watched the flight of a bright bolide. Although the weather was bad, a lot of people distinctly saw the surgeless white bright fluorescence flaming up in the south-west. It filled up all the sky and then moved from the valley of the Vitim River to the north-eastern direction. The fluorescence turned from white to blue and then to redly vinous. The flight of meteoroid was accompanied by hollow rumble and completed with a blow and shaking of the earth.

The rumble and rustling heard by multiple natives may be connected with occurrence of electric wave in the atmosphere. The variable electric field was so strong that in the apartment houses of Mama settlement, which were cut off power supply at that time, incandescent lamps began to shine dimly. Seismic stations of the Irkutsk Province recorded only feeble local shaking. Bright fluorescence at the altitude of 62 kilometers was recorded by a US satellite which tracked the fluorescence down to the 30 kilometer altitude. The satellite identified the altitude and position data of two points, based on which the Russian scientists managed to reconstruct the meteorite’s trajectory and sent several expeditions in search of it.

Nearby the lane, the researchers found a lot of broken and uprooted trees. No hurricanes took place there at that time, so the forest could be brought down only by the blast wave of meteoroid flying in the lower atmosphere. However, amplitude of the wave coming down from the altitude of 20 to 30 kilometers was unable to cause such damage. This contradiction has not been resolved by specialists yet.

The second Vitim expedition looked for cosmogeneous substance particles, which could be preserved in the snow covering tops of the hills in the area where the meteorite had fallen down. However, the researchers found only hollow spherules, their size normally not exceeding 100 to 200 mcm. Fragments of these fragile spherical components colored brown and deep-brown contain oxide and silicate minerals typical of meteorites, namely of chondrites. The researchers also found grains of nickel-containing pyrite and particles of ferriferous compounds. The spherules’ shape and peculiarities of their structure do not contradict the version that they could drop out of the dust ablative trace of meteoroid. Substances contained in the spherules can hardly be related to the rock substance in the Mamsko-Chuisk region. Since no fragments of the Vitim meteoroid have been found so far, these spherulesare are now the single probable evidence of its material composition.

Nevertheless, the researchers have not given up hopes for finding fragments of the Vitim meteoroid. Probably, the bulk of its fragments dropped out either farther along the trajectory (if the US satellite erroneously determined altitudes of two points in the falling route) or aside from the calculated path (if the two points’ position data was identified mistakenly).