Solving the riddle

In 1938 an aerial photographic survey of the Tunguska region was undertaken. Although the survey was incomplete, it showed the unique radial nature of the fallen trees. It also showed that the South Swamp was indeed the centre of some great catastrophe.

In July 1939 a 'refreshed' Kulik again returned to Tunguska to examine the South Swamp. His team started boring in several places in the swamp. The drilling showed numerous channels on the surface of the swamp. Kulik interpreted them as underwater craters. This idea was later rejected by geologists who said that this was a natural feature of the swamps in the area. However, the Academy of Sciences congratulated Kulik for his 'great persistence and enthusiasm that led to the recent concrete advance in our knowledge of the subject' and approved a fifth expedition in 1940 to conduct a magnetic survey of the South Swamp. But the expedition did not take place because of the outbreak of the Second World War.

On 5 July 1941, the day the Nazis invaded Russia, Kulik joined the Moscow People's Militia, a volunteer military unit. In October, while taking part in a battle on the front line, he was wounded in the leg and captured by the advancing German army. He was held as a prisoner of war in the town of Spas-Demensk, about 300 kilometres southwest of Moscow. He worked as a nurse in a prisoner-of-war hospital, where he contracted typhus and died on 14 April 1942. He was 58 years old. He was buried in the local cemetery. In 1960 the Academy of Sciences built a simple memorial on his grave. The plain gravestone is still there; it's simply marked: 'Kulik, Leonid Alekseyevich 1883-1942'.

Figure 9: Kulik's grave in Spas-Demensk, Russia. (Photo by Andrei Ol'khovatov, Moscow.)

'Kulik', a 58-metre diameter crater on the far side of the Moon, asteroid '2794 Kulik' and a Vanavara street named after him perpetuate the memory of the first Tunguska researcher and the founder of meteoritics in Russia.

The first expedition after the war was in 1958. In 1963 investigations gained new vigour under the leadership of Nikolai Vasilyev (1930-2001) of the Academy of Sciences, who coordinated the scientific research of 29 investigations. It wasn't until 1989 that foreign scientists were officially invited to join the Russian investigations. Now the Russian government has set aside 4,000 square kilometres of the Tunguska region as a national reserve. But the Tunguska explosion site remains inaccessible. The nearest Trans-Siberian railway station is Krasnoyarsk, 600 kilometres north of Vanavara. This tiny trading post has now grown into a small town of more than 4,000 people. From Vanavara the explosion site is about 70 kilometres, but it can be reached only by helicopter or by hiking.

Why did Kulik fail to find any meteorite fragments or impact crater in the South Swamp or the Great Cauldron? According to Krinov, careful investigation of the cauldron 'does not give any grounds for concluding that this cauldron is the place where the meteorite fell'. But four observations point to the fact that the cauldron is the site of the explosion: (1) the absence of other places in the Tunguska area which might attract attention as the possible place of the fall; (2) the Evenki people's designation of the cauldron as the place of the fall; (3) the cauldron is the epicentre of the seismic wave; and (4) the radial forest devastation around the cauldron. 'There is only one possible explanation that removes the contradiction, that is, that the meteorite did not explode on the surface of the ground, but in the air at a certain height above the cauldron', Krinov concluded.

Krinov's explanation did not solve the riddle of the Great Siberian explosion. The controversy about the Tunguska fireball continues to this day, and there is no shortage of attempts to explain the cataclysmic explosion. Igor Zotkin, a Russian expert on meteorites, once remarked: 'I doubt if there is any recent discovery that has not been called on to explain the Tunguska enigma.' Today, scientists' line-up of suspects includes a comet, a mini black hole, an asteroid, a rock of anti-matter or a mirror matter asteroid, and a methane gas blast from below. In the X-files we have an alien spacecraft, a laser beam fired by ETs in an attempt to communicate with lonely little earthlings, and an experiment on a 'death ray' which got out of hand.

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