The Tunguska Event: Still A Mystery After 107 Years
On the morning of June 30, 1908, a large fireball crossed the sky above the taiga of the Stony Tunguska (Podkamennaya Tunguska) in Siberia. A series of explosions followed, which could be heard even in the distant village of Achajewskoje about 745 miles away. Various meteorological stations in Europe recorded both seismic and atmospheric pressure waves. And during the following days, strange phenomena were observed in the sky of Europe, such as silvery, glowing clouds, colorful sunsets and a strange luminescence in the night.
Russian newspapers soon reported on this supposed meteorite impact. International newspapers speculated about a possible volcanic explosion, as memories of the eruption of Krakatoa in 1883 were still strong. However, the inaccessibility of the region and Russia’s unstable political situation prevented further investigations.
Thirteen years after the incident, Russian mineralogist Leonid Alexejewitsch Kulik became interested in the still unexplored event after reading some of the accounts about an explosion and large glowing object. He also had some hopes to recover precious extraterrestrial metals from the impact site.
Kulik travelled to the city of Kansk, where he studied reports about the event in the local archives. Many of those stories refer to large fireballs, flames and a sequence of fourteen “thunders.” In March of 1927, he arrived at the outpost of Wanawara. Then on April 13, Kulik discovered a large area of about 830 square miles covered with rotting logs – the strange “Forest of Tunguska.”
Despite exploring the entire area, Kulik and his team didn’t locate a single great crater as he’d expected, but he did find some circular pits that were interpreted as being smaller craters produced by impact fragments. However, no meteoritic material was discovered at the site.
In the fall of 1927, a preliminary report by Kulik was published in various national and international newspapers. As a result, the event of 1907 became known as the “Tunguska Event.”
Kulik formulated one of the first hypotheses to explain both the reports and lack of evidence on the ground: he suggested that an extraterrestrial solid exploded in the atmosphere, causing the observed explosion and devastation. That solid’s fragments then became buried in the swampy ground, which was too soft to preserve the typical morphology of an impact crater.
In 1934 Soviet scientists proposed a variation of Kulik’s hypothesis. They proposed that it was a comet, not a meteorite, that struck the area. Since comets are composed mostly of ice, one would have been completely vaporized during the impact, leaving no traces behind.
Over time, many other theories – some quite unusual – have been proposed to explain the apparent lack of craters in the region or the missing extraterrestrial matter.
Based on impressions left by the first atomic bombs, the Engineer Aleksander Kasantsews developed an unusual explanation involving a nuclear explosion of possible extraterrestrial origin between the years 1945 and 1959.
In 1973, American physicists proposed in the journal Nature that a small black hole had collided with earth, causing some sort of matter-antimatter explosion.
The German astrophysicist Wolfgang Kundt and later Jason Phipps Morgan of the Cornell University in Ithaca and Paola Vannucchi from the University of Florence have proposed an ulterior hypothesis in the past few years: “Verneshots.” Named for the author of the novel A Journey to the Center of the Earth, Verneshots are supercritical magma/gas mixtures that violently erupt from underground. According to this proposed model, areas with a thick crust or composed of hard rocks (the region of Tunguska is covered by the thick basalts of the Siberian Trapps) magmatic intrusions and gases tend to build up pressure until the cover is shattered to pieces. Hot gases would escape then into the atmosphere, causing a visible explosion.
However, the most compelling explanation for the Tunguska Event remains the impact of a natural extraterrestrial object. This idea is supported by the reports describing a fireball descending on the tundra, sedimentary features, like the presence of nanodiamonds, magnetic- and silicate spherules in sediments and the mapped distribution and direction of the fallen trees, which point away from the explosion site.
However, there are some inconsistencies in the idea that the Tunguska Event was of extraterrestrial origin. For example, the accounts of a series of thunders are hard to explain with a single impact. Additionally, the recovered sediments are not unambiguous – they’re also explainable also by the common contamination of sediments by extraterrestrial material, because many small meteorites are disintegrated every day in earth´s atmosphere.
In 2007, Luca Gasperini and his research team of the University of Bologna proposed that a small lake in the region, Lake Cheko, may have been the impact crater of a fragment that caused Tunguska Event. Lake Cheko is unusually deep for a region characterized by shallow ponds, which are formed by superficially melting permafrost. There’s also no record of the lake existing before 1908, however it’s also true that the region was poorly mapped and explored at the time. Gasperini’s evidence is controversial, as seen in one published answer to this research.
At this point, it’s likely that only the discovery of extraterrestrial material on the bottom of a lake would be the decisive evidence needed to solve the mystery of Tunguska.
By David Bressan, FORBES