Atmospheric scientists are in the possession of authentic evidence on what they call pseudometeorites hitting this planet in various places (Mongolia, Turkmenia, Poland and Estonia, to name but a few). Being pieces of slag pumice, their chemical composition differs considerably from that of all the familiar types of meteorites. Samples of this kind collected from 11 sites on the territory of Russia and Kazakhstan have been investigated by Dr. Ye. Dmitriev of the State R&D Center named after Khrunichev.

The studies have revealed on the surface of some of the samples traces left by high-velocity streams of hot gas. According to eyewitness reports these fragments could have dropped out from the bolides they observed and whose trajectories point to probable links with meteorite showers. The chemical composition of the samples suggests possible genetic links not only between the different finds of this kind, separated by distances of thousands of kilometers, but also between these samples and the impactites* found in meteorite craters, such as tektites-glassy bodies of probably meteoritic origin and of rounded but indefinite shape.

An unexpected result has been received from petrological analysis of the samples which bear traces of what experts call powerful electric breakdowns. The same was also discovered in phylgurites (glasses of natural terrestrial origin), tektites and certain impactites which suggests the existence of a common mechanism of their formation. Glassy fibers of complex shapes, discovered in practically all of the samples and called streamerglasses, can be regarded as the petrological traces of such electric breakdowns.

As compared with tektites, the investigated samples are less "flashed-over" and contain fragments and minerals of the parent matter: glass, plagioclase, feldspar, quarz, garnet, hornblende, titanomagnetite, ilmenite, wallostonite, pyroxene, etc.; found in one of the samples was a particle of nickelous iron (12.15% Ni). Apart from that their chemical composition is more diverse. On the strength of this evidence, Dr. Dmitriev suggested calling them subtektites (probably also including impactites with traces of electric breakdowns).

Before they reached the Earth, the subtektites and tektites must have been inclusions into the nuclei of short-lived comets. The varied composition of the inclusions and the young age of tektites point to an eruptive or explosive origin of comets. On the strength of his findings Dr. Dmitriev suggested a new hypothesis of the origin of tektites.

Tektites and subtektites are phylgurites of extraterrestrial origin produced by strong electric discharges in matter which accompany the "escape" of comet nuclei from massive heavenly bodies. Tektites are fragments of melt jets expelled from large lightning-

* Impactite - rock remelted at meteorite impact and explosion. - Ed .

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Streamerglasses extracted from:

a - tektites-moldavitos;

Ь - phykjwtos (Cameroon);

c - subtektites;

d - tektite-irgesite from Jamanshin site;

e - samples from the epicenter of the Tunguska catastrophe. In brackets-maximum particle size (mm).

conducting channels by excessive pressure of high-temperature gas. Subtektites are fragments of glassified inner walls of lightning- conducting channels torn apart by inner gas pressure.

And since the latter are "molten through", or fused, to a lesser extent, they carry considerably more data on the properties of comet-generating heavenly bodies and the processes on their surface and within them. The meteorite classification should be augmented with a group of comet meteorites which include tektites and subtektites and their parent matter and also certain types of iron meteorites.

Dr. Dmitriev developed a method of isolating with the help of streamerglass of comet matter from astroblems, impact craters and the soil in the areas of atmospheric explositions of major bolides.

As was earlier suggested, the Tunguska meteorite was but a fragment of the nucleus of a big eruptive comet and the fallout matter in the impact area possessed differentiated composition little different from terrestrial sedimentary and volcanic rock. In support of this hypothesis experts examined according to a proposed procedure samples of soil and peat from the epicenter of the catastrophe. They found large amounts of comet particles - streamerglasses and subtektites, which makes it possible to speak of a massive fall-out of finely dispersed and fractured, or crushed, matter in the epicenter of the blast.

Ye. Dmitriev, Tektites, Subtektites, Streamerglasses and the Tunguska Meteorite, PRIRODA, No. 1, 2000

Prepared by Vladimir GOLDMAN

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