On dust trails of fireballs

By Alexandra Terentjeva and Ilya Kurenya

Abstract: A meteor dust trail is a very rare natural phenomenon. Its occurrence requires penetration of a large meteoroid body deeply enough into the atmosphere. There is only one dust trail per 250 persistent gas trails in the personal archive of I. S. Astapovich (1956). Dust trails, as a rule, indicate meteorite falls.

 

Introduction

“The dust trail of a meteor is a rare phenomenon of nature”, writes I. S. Astapovich (1956). “Unlike gas trails, visible only at night, dust trails are visible only in the daytime or at dusk. They appear during the flight of large fireballs, which penetrated low in the atmosphere. Against a light sky background, they, like ordinary clouds, can look both light and dark, depending on the illumination by sunlight. Projected against the background of evening glow, they will look almost black if they lie in the shadow of the Earth, or extremely bright, as if burning hot, if these trails are illuminated by the direct rays of the Sun at the heights where they are located. If at this time the Sun is below the observer’s horizon and twilight has come, their light may be so bright as to produce shadows from terrestrial objects. In a few seconds, the initially straight-line trail seems jagged under the influence of air currents and then more and more curved, resembling a frozen lightning, until it is scattered away by winds. At the same time the trail expands, spreads, fades, turns into one or more shapeless clouds, sometimes stretched in the direction of their movement, and takes 30–60 minutes, or sometimes several hours, to dissipate completely”.

The most thorough study of gas and dust trails of meteors is presented in the works by I. S. Astapovich (1956, 1958, 1966, etc.), which apparently remain little known or completely unknown to the Western reader. I. S. Astapovich gives an extensive series of his own observations of meteor trails coming from systematic year-round observations in 1942–1960. The observations were made in Ashkhabad, near Firyuza (38 km from Ashkhabad) and in Odessa. A total of 150 meteor trails were found during 1377 hours of observations. It is interesting that for 250 persistent gas trails in the personal archive of I. S. Astapovich there is only one dust trail, and even then, found outside the observation program (Astapovich, 1956). Therefore, it is impossible to make systematic natural observations of dust trails at any point, as the number of such trails will be one or zero for several decades.

On some exceptional dust trails

Speaking about the history of study of dust trails, I. S. Astapovich (1956) gives a number of remarkable examples. Some of them are worth highlighting. A remarkable specimen of a dust trail was given by the Boguslavka meteorite, which fell on 5/18 October 1916 in the Primorskaya region near the Chinese Eastern Railway station Grodekovo-Khorvatovo. “On the horizon … a thick black cloud of smoke. This trail was visible 350 kilometers away in China … The trail was quite impressive. As the fireball travelled, jets of fire could be seen bursting now and then through the thick misty trail. The found meteorites, two of which are in the collection of the USSR Academy of Sciences, and the third is in Japan, with a total weight of more than a quarter of a ton, were iron. Thus, dust trails are produced not only by stone, but also iron meteorites”.

An exceptionally intense dust trail was left behind by a bright fireball –15m, which was visible over an area of six regions from Moscow to Penza. It occurred on 24 September 1948. In 20 minutes, air currents already gave it the appearance of a line of double curvature. In some places it was projected into the sky shaped as a giant number “3”. The trail attracted the attention of numerous witnesses. A detailed processing of observations of this interesting fireball was made by V. V. Fedynsky (1955) from the materials of the Committee on Meteorites of the Academy of Sciences of the USSR. Its trajectory in the atmosphere and its orbit were determined accurately enough. The meteoroid body with a mass of 250 kg moved along an elliptical orbit slightly inclined to the ecliptic plane (i = 7.5°). The small geocentric velocity of the meteoroid body, which was catching up with the Earth, accounted for a relatively low altitude of the emergence of the fireball (85 km). The mass of the meteoroid body completely vaporized and dispersed above 62 km, which explains the absence of sounds and meteorite fallout.

 

Finally, we will briefly mention a particularly interesting trail of the famous Sikhote-Alin iron meteorite on 12 February 1947. “The trail stretched to the very surface of the Earth, as the meteorite had a large mass and hit the ground at a speed of 0.5–1 km/s with a stream of pieces… Its trail was broad, smoky, bubbling and curling and lasted until evening, that is about 8 hours” (Astapovich, 1956).

In 1907, Trowbridge began to study meteor trails. He showed that gas trails appear above 82 km while dust trails mainly at 64 km or lower. They are especially frequent at the altitude of 40 km and rare above 64 km (up to 80 km) (Astapovich, 1956).

Conclusion

By special observations in the glowing sky in 1955 in Ashkhabad (Terentjeva, 1956) it was found that ordinary meteors do not produce dust trails. “This is both because of their low mass and because they transform into meteor gas but not into dust. To make a dust trail, a meteor body must be large enough (a fireball) to penetrate rather dense layers of the atmosphere. Therefore, as a rule, dust trails emerge in meteorite falls”, I. S. Astapovich wrote in his monograph (1958).

Thus, based on everything stated above, we can say that dust trails indicate meteorite falls. Hence, meteor observers having detected a dust trail should calculate the geographic coordinates of the ground point in the vicinity of which a meteorite or its fragments may have fallen.

We take this opportunity to present in this article a photograph of the outstanding scientist, Corresponding Member of the USSR Academy of Sciences, Laureate of the USSR State Prize V.V. Fedynsky (Figure 1). His main works relate to the field of exploration geophysics, gravimetry, Earth physics and meteor astronomy. In meteor astronomy he contributed to the organization of systematic photographic, spectral, and radar observations of meteors in the USSR. A submarine ridge in the Indian Ocean and the minor planet No. 1984 are named after him.

Corr. member V. V. Fedynsky had a long-standing friendship with Prof. I. S. Astapovich. Visiting I. S. Astapovich at his flat in Kiev, V. V. Fedynsky said: “Forty years of friendship were not overshadowed by anything”. Both remarkable scientists were born in the same year of 1908 (the fall of the Tunguska meteorite) and passed away almost simultaneously (V. V. Fedynsky died two years after I. S. Astapovich).

Acknowledgment

This paper was translated into English by I. Kurenya. The authors thank Paul Roggemans for his efforts enabling the preparation and publication of this paper.

References

Astapovich I. S. (1956). “Dust trails of fireballs”. Proceedings of the Turkmen State University. Issue VI, 35–48. (In Russian).

Astapovich I. S. (1958). “Meteor phenomena in the Earth’s atmosphere”. Fizmatgiz. (In Russian).

Astapovich I. S. (1966). “Some results of visual observations of meteor trails”. Results of researches of international geophysical projects: Meteor Investigations. No. 1. Publishing House “Nauka”, Moscow, pages 7–61. (In Russian).

Terentjeva A. K. (1956). “Telescopic observations of meteors in the glowing sky”. Astron. Tsirk. AN SSSR, No. 169, 16–17. (In Russian).

Fedynsky V. V. (1955). “A fireball with a bright trail on 24 September 1948”. Meteoritics. AN SSSR, Issue XII, 14–28. (In Russian).