First fragments from 1908 Tunguska Event may have been found

A Russian scientist may have found the first fragments of the object that caused the 1908 Tunguska Event, and this may finally put to rest the enduring mystery of what caused the event.

In the early morning of June 30th, 1908, something big entered the Earth's atmosphere over Siberia and exploded. The shock wave from the blast leveled trees over an area of about 2,000 square kilometres, and people living hundreds of kilometres away reported being knocked from their feet and windows being shattered. It's estimated that the explosion was the equivalent of a 10-15 megaton bomb, and the tremor from the explosion was roughly equal to a magnitude 5.0 earthquake.

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There were no direct witnesses to the blast, though, so exactly what caused the event has remained a mystery. Some of the more wild speculations for this over the years include a crashing UFO, a chunk of antimatter falling from space, a black hole, a natural gas explosion, or a 'natural H-bomb'. Some even say that an alien ship intercepted a comet in mid-air, to save the Earth from an impact that would have destroyed humanity.

The more likely cause of the event is from either a comet or an asteroid entering the atmosphere and exploding in mid-air, similar to a more recent event in the same general area back in February. However, although expeditions to the area have turned up some evidence — such as tiny metallic spheres (possible 'shrapnel' from the object) and even a ground-penetrating radar view of a possible impact crater (complete with large ice shards buried deep down) — noone had reported finding any large fragments at the surface though, so reasoned cases continue to be made for either case (comet or asteroid), and the debate has gone on for years.

Now, Andrei Zlobin, of the Vernadsky State Geological Museum in Moscow, believes that he has found the first fragments of the object that caused the event.

He explored the area in 1988, digging into the sediments at the crater site, but finding nothing there he switched to sifting through the rocks on the bed of the nearby Khushmo River, and managed to collect a hundred or so that he found interesting enough to warrant further examination.

However, upon returning to Moscow, those rocks gathered dust for the next 20 years, until 2008, when he finally went back to them and turned up three that showed signs of melting and what are called 'regmaglypts' — which are impressions in the rock that look similar to what happens when you press your thumb into a lump of clay.

He named the rocks 'dental crown' (1), 'whale' (2) and 'boat' (3), due to their shapes. 'Whale' is the largest, at about 3 centimetres across and a mass of over 10 grams.

Now, Zlobin isn't making any definite claims about this yet. Chemical analysis of the rocks is still needed, to be sure that they're of extraterrestrial origin. Even then, it still may not prove the case between comet and asteroid, since comets can contain fragments of rock. According to The Physics arXiv Blog, Zlobin definitely favours the comet explanation, since he has already made calculations of the original object's density that suggest it was similar to Haley's comet.

As for why it took him 20 years to get back to these specimens... the arXiv Blog has an idea about that too: "It's not hard to imagine that the political changes that engulfed the Soviet Union in the year after his expedition may have played a role in this, but it still requires some explaining." I have to agree. Going through the major social upheaval of "the Fall of Communism" likely counts as a valid enough distraction from this kind of work.

The title of Zlobin's research paper is Discovery of probably Tunguska meteorites at the bottom of Khushmo river's shoal, which was published on the site on April 29th.

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Of all the possible causes of the 1908 Tunguska Event, the most enduring one in my mind is the 'interdimensional cross rip' that Dr. Ray Stantz refers to at the end of Ghostbusters (even though he got the year wrong). However, that more fantastical explanation aside, it's exciting whenever anyone turns up any new evidence for what caused the event. I'm waiting for someone to go back to dig up the crater they took images of back in 2010, but hopefully Zlobin's fragments will give us something interesting to work with until then.

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