The third Tunguska expedition

The third expedition left Leningrad in February 1929 and returned in October 1930. It was a much larger undertaking which included many scientists. Among

Figure 8: Map of the Tunguska site produced from the visual survey during Kulik's third expedition in 1929-30. (Key: 1 - devastated forest; 2 - meteorite impact site; 3 - survey points; 4 - track; 5 - road to Strelka trading station; 6 - limit of scorched area; 7 - limit of forest devastation; 8 - limit of the effect of the explosive wave.) (Courtesy Marek Zbik, University of South Australia.)

Figure 8: Map of the Tunguska site produced from the visual survey during Kulik's third expedition in 1929-30. (Key: 1 - devastated forest; 2 - meteorite impact site; 3 - survey points; 4 - track; 5 - road to Strelka trading station; 6 - limit of scorched area; 7 - limit of forest devastation; 8 - limit of the effect of the explosive wave.) (Courtesy Marek Zbik, University of South Australia.)

them was young Krinov (who lost a toe to frostbite on the expedition and who would become the Chairman of the Committee on Meteorites of the Academy of Sciences). The expedition was also well equipped. A horse train of fifty carts carried drilling machines, water pumps, geological, meteorological and surveying instruments, cameras, field tools and other supplies from Taishet, the last station on the Trans-Siberian railways, to the Tunguska site.

Kulik was convinced that the Suslov crater and a chain of craters around it were formed by the fall of separate large meteorite pieces. He decided to dig the Suslov crater first, his team drilling a 4-metre hole in it. The digging of this hole took Kulik's men one month's hard work, but they did not find any impact features. The walls showed only undisturbed material. However, they found a decayed tree stump at the bottom of the hole, suggesting that the crater was not caused by the impact of a piece of the meteorite after it broke on hitting Earth. 'Indeed, it was impossible to imagine that a tree stump could have been presented in a natural position so near the centre of the hole formed by the fall of a meteorite', Krinov noted.

Krinov, who had been making an independent survey of the area, concluded that the epicentre of the fall did not lie on the northern border of the basin, the location of the Suslov crater, as believed by Kulik. He suggested that the exact location of the epicentre was South Swamp, an area a few kilometres south of the Suslov crater. Krinov's suggestion made Kulik angry and he excluded him from further work on the expedition.

Kulik's belief in his Suslov crater hypothesis was unshakeable. He directed his men to set the drilling rig at the edge of the crater. They continued digging during the frigid winter months and drilled one hole 34 metres deep and 4 metres wide in the solid frozen ground. Still they did not find any meteorite material. Kulik's spirits soared when a worker found a piece of glass in the hole. Kulik concluded that it was an impactite, a rock fused into glass by the impact of the meteorite. But the glass did not turn out to be the smoking gun Kulik was looking for. It was, in fact, a piece of a bottle shattered during a fire which broke out in one of the huts on the first night of the expedition. 'Unfortunately this fragment was mentioned in several articles by Kulik as a find of silica glass, and even today it misleads researchers', Krinov said.

Two more holes were drilled before Kulik gave up drilling on 1 March 1930. He finally concluded that the Suslov crater was not a meteorite crater. Kulik learned the hard way what is now known to every student of meteoritics: finding a meteorite crater may not be as simple as finding a hole in the ground.

Six months later Kulik returned to Leningrad 'with grey hair and ruined health'. J.G. Crowther, a British science journalist who interviewed Kulik after the third expedition, wrote in Scientific American (May 1931): 'Professor Kulik's expeditions have left a mark on him. He is a tall, wiry, bronzed man of Scots figure, lean and a little tired. Perhaps a rest will soon entirely refresh him.'

Crowther's hope turned out to be a prophesy. Kulik was not to return to Tunguska for another seven years, but he continued working on the project. He also apologised to Krinov and requested him to continue working with him. Like Krinov, he now believed that the South Swamp was indeed the blast's centre.

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