26Jun2015

The Tunguska Meteorite Anniversary

 Explosion
On 30 June 1908 a mysterious explosion rocked the Jenissei portion of the Siberian forest. People living in the area observed a huge fireball that rose up high in the sky and never forgot the sight.

Russian scientist Kazantsev researched what he described as the Tunguska blast, going so far as trailblazing through the area in search of an impact crater that was never found. Trees in the area, though, were knocked to the ground from an epicenter which, unlike normal blasts, was more elliptical than spherical, following the original object’s trajectory.

Many wild theories have been suggested as to what caused the blast. Most prevalent among those have been microscopic black hole impact with the Earth, collision with a comet and a nuclear powered extraterrestrial vehicle losing control and crashing. Both are extremes, logic suggets a natural occurence.What we know is this.

At 7.00am on 30th June 1908 near the lower Tunguska River, Siberia, a large explosion occurred. The explosion was so massive that it caused damage 400 miles away, and was heard even further. Even the heat that came out from the explosion was felt hundreds of miles away. For several nights all over northern Europe, the sky glowed enough to light the street of London. At first it was assumed that a massive meteorite had collided with the earth.

Map location of the 1908 Tunguska explosion in Siberia

Given the remoteness of the area it was not until 1927 that an expedition was mounted to investigate the crash area. The expedition could not locate any bits of meteorite which puzzled them due the size that the meteorite would have to have been to create such a large explosion. Another puzzle for the expedition was the way the tress were felled in an outward motion and that in the centre an area of trees were still standing, although all their bark and branches have been destroyed.

After the Second World War and the bombing of Hiroshima and Nagasaki, photos of the cities were compared with aerial photos of the Tunguska blast, and they were stunning similar. As a result of this various scientists speculated that a nuclear explosion had taken place over the area, hence explaining the tree formation, and because no nation possessed nuclear device the logical conclusion was that it was from an exploding alien nuclear powered craft.This “Tunguska Event” is probably related to the impact with the Earth of a cosmic body that exploded about 5–10 km above ground, releasing in the atmosphere 10–15 Mton of energy.

Other theories started to be banded around ranging from pinpoint black holes, and antimatter particles. Many of the witnesses to the original crash spoke of seeing and oval-shaped mass moving across the sky, as well as seeing the object change course, and of having a very low speed. Most people today believe that what hit Tunguska was simply a meteorite or comet, not a ‘spaceship.’  This “Tunguska Event” is probably related to the impact with the Earth of a cosmic body that exploded about 5–10 km above ground, releasing in the atmosphere 10–15 Mton of energy. Adapted from UFO Evidence

Selected Eyewitness Reports

Testimony of S. Semenov, as recorded by Leonid Kulik’s expedition in 1930.“At breakfast time I was sitting by the house at Vanavara trading post (65 kilometres/40 miles south of the explosion), facing North. […] I suddenly saw that directly to the North, over Onkoul’s Tunguska road, the sky split in two and fire appeared high and wide over the forest (as Semenov showed, about 50 degrees up – expedition note). The split in the sky grew larger, and the entire Northern side was covered with fire. At that moment I became so hot that I couldn’t bear it, as if my shirt was on fire; from the northern side, where the fire was, came strong heat.

I wanted to tear off my shirt and throw it down, but then the sky shut closed, and a strong thump sounded, and I was thrown a few yards. I lost my senses for a moment, but then my wife ran out and led me to the house. After that such noise came, as if rocks were falling or cannons were firing, the earth shook, and when I was on the ground, I pressed my head down, fearing rocks would smash it. When the sky opened up, hot wind raced between the houses, like from cannons, which left traces in the ground like pathways, and it damaged some crops. Later we saw that many windows were shattered, and in the barn a part of the iron lock snapped.”

Testimony of Chuchan of Shanyagir tribe, as recorded by I.M.Suslov in 1926.“We had a hut by the river with my brother Chekaren. We were sleeping. Suddenly we both woke up at the same time. Somebody shoved us. We heard whistling and felt strong wind. Chekaren said, ‘Can you hear all those birds flying overhead?’ We were both in the hut, couldn’t see what was going on outside. Suddenly, I got shoved again, this time so hard I fell into the fire. I got scared. Chekaren got scared too. We started crying out for father, mother, brother, but no one answered. There was noise beyond the hut, we could hear trees falling down. Me and Chekaren got out of our sleeping bags and wanted to run out, but then the thunder struck. This was the first thunder. The Earth began to move and rock, wind hit our hut and knocked it over.

My body was pushed down by sticks, but my head was in the clear. Then I saw a wonder: trees were falling, the branches were on fire, it became mighty bright, how can I say this, as if there was a second sun, my eyes were hurting, I even closed them. It was like what the Russians call lightning. And immediately there was a loud thunderclap. This was the second thunder. The morning was sunny, there were no clouds, our Sun was shining brightly as usual, and suddenly there came a second one!“Me and Chekaren had some difficulty getting under from the remains of our hut. Then we saw that above, but in a different place, there was another flash, and loud thunder came.

This was the third thunder strike. Wind came again, knocked us off our feet, struck against the fallen trees.“We looked at the fallen trees, watched the tree tops get snapped off, watched the fires. Suddenly Chekaren yelled ‘Look up’ and pointed with his hand. I looked there and saw another flash, and it made another thunder. But the noise was less than before. This was the fourth strike, like normal thunder. “Now I remember well there was also one more thunder strike, but it was small, and somewhere far away, where the Sun goes to sleep.”

Sibir newspaper, July 2, 1908“On the 17th of June, around 9 in the AM, we observed an unusual natural occurrence. In the N Karelinski village (200 verst N of Kirensk) the peasants saw to the North-West, rather high above the horizon, some strangely bright (impossible to look at) bluish-white heavenly body, which for 10 minutes moved downwards. The body appeared as a “pipe”, i.e. a cylinder. The sky was cloudless, only a small dark cloud was observed in the general direction of the bright body.

It was hot and dry. As the body neared the ground (forest), the bright body seemed to smudge, and then turned into a giant billow of black smoke, and a loud knocking (not thunder) was heard, as if large stones were falling, or artillery was fired. All buildings shook. At the same time the cloud began emitting flames of uncertain shapes. All villagers were stricken with panic and took to the streets, women cried, thinking it was the end of the world. “The author of these lines was meantime in the forest about 6 verst N of Kirensk, and heard to the NE some kind of artillery barrage, that repeated in intervals of 15 minutes at least 10 times. In Kirensk in a few buildings in the walls facing north-east window glass shook.”

Siberian Life newspaper, July 27, 1908“When the meteorite fell, strong tremors in the ground were observed, and near the Lovat village of the Kansk uezd two strong explosions were heard, as if from large-caliber artillery.” 

Krasnoyaretz newspaper, July 13, 1908“Kezhemskoe village. On the 17th an unusual atmospheric event was observed. At 7:43 the noise akin to a strong wind was heard. Immediately afterwards a horrific thump sounded, followed by an earthquake which literally shook the buildings, as if they were hit by a large log or a heavy rock. The first thump was followed by a second, and then a third. Then – the interval between the first and the third thumps were accompanied by an unusual underground rattle, similar to a railway upon which dozens of trains are travelling at the same time.

Afterwards for 5 to 6 minutes an exact likeness of artillery fire was heard: 50 to 60 salvoes in short, equal intervals, which got progressively weaker. After 1.5 – 2 minutes after one of the “barrages” six more thumps were heard, like cannon firing, but individual, loud, and accompanied by tremors. “The sky, at the first sight, appeared to be clear. There was no wind and no clouds. However upon closer inspection to the North, i.e. where most of the thumps were heard, a kind of an ashen cloud was seen near the horizon which kept getting smaller and more transparent, and possibly by around 2-3 p.m. completely disappeared.”

Tunguska Meteorite Fragments Found

http://l.yimg.com/bt/api/res/1.2/g0OuaWpHtOUM2DjL9IyZdw--/YXBwaWQ9eW5ld3M7cT04NQ--/http://mit.zenfs.com/1555/2013/05/TUNGUSKA-EVENT.jpg

A researcher digs in the peat of the Tunguska region in 1988

The region is so isolated, however, that historians recorded only one death and just handful of eyewitness reports from nearby. But the most mysterious aspect of this explosion is that it left no crater and scientists have long argued over what could have caused it. The generally accepted theory is that the explosion was the result of a meteorite or comet exploding in the Earth’s atmosphere. That could have caused an explosion of this magnitude without leaving a crater. Such an event would almost certainly have showered the region in fragments of the parent body but no convincing evidence has ever emerged.

In the 1930s, an expedition to the region led by the Russian mineralogist Leonid Kulik returned with a sample of melted glassy rock containing bubbles. Kulik considered this evidence of an impact event. But the sample was somehow lost and has never undergone modern analysis. As such, there is no current evidence of an impact in the form of meteorites.

That changes today with the extraordinary announcement by Andrei Zlobin from the Russian Academy of Sciences that he has found three rocks from the Tunguska region with the telltale characteristics of meteorites. If he is right, these rocks could finally help solve once and for all what kind of object struck Earth all those years ago.

Trees knocked over by the Tunguska blast

Trees knocked over by the Tunguska blast (Photo credit: Wikipedia)

Zlobin’s story is remarkable in a number of ways. The area of greatest interest for meteor scientists is called the Suslov depression, which lies directly beneath the location of the air blast and is the place where meteorite debris was most likely to fall.  Dig into the peat bogs here and you can easily find layers that show clear evidence of the explosion. Zlobin said he dug more than ten prospect holes in the hope of finding meteorite fragments, but without success.

Andrei Zlobin digs in the peat of the Tunguska region in 1988However, he had more luck exploring the bed of the local Khushmo River, where stones are likely to collect over a long period of time. He collected around 100 interesting specimens and returned to Moscow with them.  This expedition took place in 1988 and for some unexplained reason, Zlobin waited 20 years to examine his haul in detail. But in 2008, he sorted the collection and found three stones with clear evidence of melting and regmalypts, thumblike impressions found on the surface of meteorites which are caused by ablation as the hot rock falls through the atmosphere at high speed.

Zlobin and others have used tree ring evidence to estimate the temperatures that the blast created on the ground and says that these were not high enough to melt rocks on the surface. However, the fireball in the Earth’s atmosphere would have been hot enough for this.  So Zlobin concludes that the rocks must be fragments of whatever body collided with Earth that day.  Zlobin has not yet carried out a detailed chemical analysis of the rocks that would reveal their chemical and isotopic composition. So the world will have to wait for this to get a better idea of the nature of the body.

However, the stony fragments do not rule out a comet since the nucleus could easily contain rock fragments, says Zlobin. Indeed he has calculated that the density of the impactor must have been about 0.6 grams per cubic centimetre, which is about the same as nucleus of Halley’s comet. Zlobin says that together the evidence seems “excellent confirmation of cometary origin of the Tunguska impact.”

Clearly there is more work to be done here, particularly the chemical analysis perhaps with international cooperation and corroboration.  Then there is also the puzzle of why Zlobin has waited so long to analyse his samples. 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.

Nevertheless, this has the potential to help clear up one of the outstanding mysteries of the 20th century and finally determine the origin of the largest Earth impact in recorded history. Credit: technologyreview.com

 

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