Tunguska: meteor of the century

THE UNIQUE CASE OF COSMIC DEVASTATION IN MODERN TIMES: TUNGUSKA: METEOR OF THE CENTURY

A little over 100 years ago, on 1 July 1908, Katharine Stephen, from Godmanchester, Huntingdon, Great Britain, sent the following letter to the newspaper "The Times" of London: "I should be interested in hearing whether others of your readers observed the strange light in the sky which was seen here last night by my sister and myself."

The letter continues: "I do not know when it first appeared; we saw it between 12 o’clock (midnight) and 12:15 a.m. It was in the northeast and of a bright flame-colour like the light of sunrise or sunset. The sky, for some distance above the light, which appeared to be on the horizon, was blue as in the daytime, with bands of light cloud of a pinkish colour floating across it at intervals. Only the brightest stars could be seen in any part of the sky, though it was an almost cloudless night. It was possible to read large print indoors, and the hands of the clock in my room were quite distinct. An hour later, at about 1:30 a.m., the room was quite light, as if it had been day; the light in the sky was then more dispersed and was a fainter yellow."

Years passed however and this event, never seen before, was being forgotten.

In 1921, at the Museum of Mineralogy of St. Petersburg, Russia, naturalist Leonid Kulik was appointed head of the Meteorites Section. One of his first tasks was to investigate meteorites that have fallen into the Soviet Union. Thus began to go through his hands old newspapers from distant Siberia. Many, from 1908 contained the intriguing news that something of a definitely major scale had happened in that region of his vast country. For example, one S. Kulesh, at north of the town of Kirensk, reported to the newspaper "Sibir'", of Irkutsk (the one published between 1906 and 1918), edition of 2 July 1908, Julian calendar (July 15 in our Gregorian calendar):

"On the morning of 17 June [30 June], just after 9 A.M., some sort of unusual natural phenomenon was observed in our area. In the settlement of N[izhne]-Karelinsk (about 200 versts [214 km] to the north of Kirensk) the peasants saw in the northwest, quite high above the horizon, some sort of body glowing with an extraordinarily intense (such that you couldn’t look at it) blue-white light, moving downwards from above over the course of 10 minutes. The body took the form of a “pipe” [or tube], i.e., cylindrical. The sky was cloudless, only low on the horizon on the same side on which the luminous body was observed, there was noted a small dark cloud. It was hot, dry. Nearing the ground (the forest), it was as if the shining body spread out, in its place there formed an enormous puff of black smoke and there was heard an extraordinarily powerful rumble (not thunder), as if from large falling stones or cannon fire. All the structures shook. At the same time a flame of undetermined form began to break out of the cloud." (Reproduced by N. V. Vasiliev, A. F. Kovalievskii, S. A. Razin, L. E. Ehpiktetova, "Pokazaniia Ochevidtsev Tunguskogo Padeniia" ["Eyewitness accounts of the Tunguska impact"], Monograph, Tomsk State University, Tomsk, 1981, citing E. L. Krinov [who worked with Kulik], "The Tunguska meteorite", Publishing House of the Academy of Sciences of the U.S.S.R., Moscow, 1949. Paragraph translated from Russian by Bill DeSmedt / Copyright 2004 © Amber Productions, Inc.).

When the event of 1908 became clear to him, Kulik took the Trans-Siberian Railway and reached the town of Kansk. Gathering information from the locals, by 1922 he got estimate that the object fell on the region of the Stony Tunguska River, near a river that flows into it from the right bank, the Vanavara, specifically in a small tributary of the left bank of the latter, the Ogniya river. This place was located about 600 km further ahead. (Kulik, 1922, 1923, 1927, cited by Giuseppe Longo in "The Tunguska event", chapter 18 of the book "Comets/asteroids impacts and Human society. An interdisciplinary approach", edited by Peter Bobrowsky and Hans Rickman, Springer, Berlin, 2007).

Five years later, in 1927, Kulik returned to Siberia, now in command of a well-prepared expedition.

Ethnographer Innokentiy Suslov, who also was exploring this region, but in order to learn more about the Tungush native people, heard in 1926 this creepy story from Chuchana Stepan, of the Shanyagir clan, in the Strelka-Chunya trading post, who, along with his brother Chekaren, conversed with him ("Questioning witnesses in 1926 about the Tunguska catastrophe", in the collection "The problem of the Tunguska meteorite", Tomsk State University Publishing House, Tomsk, 1967, pages 21-30, reproduced by Vasiliev and others, cited work, paragraphs translated from Russian by DeSmedt, cited above):

"Our 'choum' [sort of tent of conical shape] stood on the banks of the Avarkitta. Before sunrise Chekaren and I arrived from the Dilyushmo creek, where we had stayed with Ivan and Akulina [Lyuchetkan]. We fell into a deep sleep. Suddenly we both woke up at once: someone had jogged us awake. We heard a whistle and felt a strong wind. Chekaren yelled to me “Do you hear how many golden-eyes [species of duck: "Bucephala clangula"] or mergansers are flying by?” We were both still in the 'choum', you know, and we couldn’t see what was going on in the forest. Suddenly someone shoved me again, so hard that I hit the 'choum's' pole and then fell on the hot coals in the hearth. I got scared. Chekaren also got scared, caught hold of the pole. We began to yell father, mother, brother, but no one answered. Beyond the 'choum' there was some sort of noise, we could hear how the tree-trunks were falling. Chekaren and I crawled out of our sleeping bags and already wanted to leap out of the 'choum', but suddenly the thunder struck very strongly. That was the first thunderclap."

"The ground began to twitch and pitch, a strong wind slammed into our 'choum' and knocked it over. I was squeezed hard by the poles, but my head was not covered because the 'ellyun' [kind of canvas] had split. There I caught sight of a terrifying marvel: The tree-trunks are falling, their needles are burning, the dried ones on the ground are burning, the reindeer moss is burning. There’s smoke all around, my eyes hurt, it’s very hot, I could burn up."

"Suddenly, above the mountain, where the forest had already fallen, something started to shine intensely, and, I tell you, it was as if a second sun had appeared"

Leonid Kulik, armed with these stories, began his second expedition in the spring, in a futile attempt to get there before the region became a mosquito-infested swamp. From the remote Taishet railway station, he used horse sleds until reaching Keshma, where they packed more supplies. From there it took them until the end of March to reach the small town of Vanavara, on the Stony Tunguska River. This was the last post of civilization before entering the swampy forests where Kulik estimated the meteor had fallen, tens of kilometers ahead.

The first attempt to reach the site ended quickly because of a heavy snowstorm. They had to return to Vanavara.

The second attempt began on 18 April 1927. Three days later they came to the river Chamb'e, where they changed their horses by reindeer. By then Kulik and his assistants were already in bad shape, due to infections and the lack of adequate food.

They followed the Chamb'e for two days until they reached the river Makirta, where they saw the first signs of the explosion of almost 20 years ago. They continued to move north, to where they believed the center of the devastation was.

Often they had to hack their way through the branches of fallen trees. Kulik noticed that the tops of the trees were burned, by something that might seem a sudden flash. The sinister place terrorized the native guides, who refused to follow. Kulik had to return back to Vanavara.

On 20 April, Kulik and two (new) guides started the third attempt. This time they built river rafts to have better mobility. So they came up near the desired location. They continued on foot, and on 20 May 1927 Leonid Kulik and his people finally came to a forest completely demolished, flat, horizontal. After a week of walking inward, they set up camp. Kulik believed that the crater he was looking for should be very close. From this camp he made several expeditions until having finished walking around in a full circle around the area. He found that all the trees pointed outward, radially, so he sought what would be the center. Of course he expected to find a crater, but instead, in the place he called "the Southern Swamp", he found himself facing the strange spectacle of a group of trees burned but still standing, their branches torn, as if they were columns, right in the middle of all this devastation.

Kulik led other expeditions to Tunguska, between 1929 and 1938. In the last he even got to do an extensive mapping of the place by aerial photography. But despite his efforts, he never managed to find his gigantic meteorite.

In 1946, theorist Aleksandr Kazantsev suggested that the lack of fragments or craters in Tunguska were indications that the explosion happened in the air.

Finally, in 1958 and 1961 the Academy of Sciences of the Soviet Union organized the first major multidisciplinary expeditions to Tunguska, with hundreds of members, using helicopters and all kinds of support matériel. There were other important expeditions in 1959 and 1960, and nine expeditions until 1979. With the fall of Communism Western researchers began to arrive in good numbers.

One of the problems to be solved was why a body with enough mass to cause such a great explosion failed to reach the ground, having been slowed by the atmosphere. For example, a comet would not come to the ground, being less dense than an asteroid, but that is exactly why it would not release as much energy as detected by seismographs and barographs throughout Europe and Asia on 30 June 1908.

In 1994 a team led by Giuseppe Longo finally got to isolate, in the resin of trees that suffered the explosion, tiny solid grains. The analysis by X-ray spectrometer showed chemical elements typical of stony asteroids, though there is much to be done.

Most assumptions about Tunguska presumed that the explosion was unleashed instantaneously starting from a point in the center. However, in 1997 Mark Boslough and David Crawford, after observing the collision of comet D/1993 F2 (Shoemaker-Levy 9) with Jupiter in 1994, proposed a model in which the body disintegrates as it enters the atmosphere, until finally what hits the ground is a mass of hot gases, sufficient to cause all the damage seen in those woods. And how big was that drifting space body? In the case of Tunguska, some tens of meters. Something common and routinary in the vastness of the Solar System.

Aldo Loup.

Originally published in ABC Color, on 3 August 2008. Photograph: Extraordinary spectacle of a forest in horizontal position, Tunguska, Siberia, U.S.S.R., 1927. An estimated 80 million trees were knocked down by the Tunguska meteor. Credit: Expedition of 1927, led by Leonid Kulik, Academy of Sciences of the U.S.S.R..