First expedition to depths of Lake Cheko close to epicentre of Tunguska event to start in February

Russian scientists will be travelling to the remote Tungussky nature reserve in Krasnoyarsk region, Central Siberia, at the end of February. 

A team of four received a permit to dive below 30 metres; this would be the first research at Lake Cheko at such depth. The winter expedition will start a cycle of long-term research, said Evgenia Karnoukhova, the senior inspector at the Tungussky reserve.

‘Lake Cheko is 54-metres deep. The team of researchers aim to study how thick the lake bottom’s sediments are, and take primary samples. The data they’ll gather will be analysed and passed on to geologists. We are not speaking about the search of any celestial body at this stage’, Evgenia said. 

Twisted trees and starry sky close to the epicentre of the Tunguska event in Siberia; Evgenia Karnoukhova, the senior inspector at the Tungussky reserve. Pictures: Evgenia Karnoukhova

The so-called Tunguska event, nearly 109 years ago, is still a challenge for modern science, and the subject of sharp disagreement among researchers. 

One of the key questions since the first expedition led by Russian mineralogist Leonid Kulik is: if it was a meteorite, where is the crater, and the extraterrestrial matter?

In 2012 a research team from Italy's University of Bologna led by Luca Gasperini pointed to a small bowl-shaped 500-metre diameter Lake Cheko as the impact crater. It is located some 8 km from the supposed ground zero of the Tungiska Event; it had not been marked on maps previously; seismic measurements of its bottom indicated that sediment had been building for around a century; and that the depth of the lake - which is shaped like a crater - was deeper than is typical for the region.

They also concluded there is dense stony matter beneath the floor and sediment, the 'remnant' of the exploding meteorite. 

The team reported that seismic reflection and magnetic data revealed an anomaly close to the lake's centre, less than 10 metres below the floor. This anomaly was compatible with the presence of a buried stony object and supports the notion Cheko is an impact crater lake, they concluded.

In 2017 this theory was strongly disputed by Russian scientists, who said the area was badly mapped and there was no surprise Lake Cheko wasn’t on the old maps.

Researchers from Krasnoyarsk and Novosibirsk assessed the age by analysing its bottom sediments, undertaking geochemical and biochemical analysis. 

Their colleagues from the Institute of Geology and Mineralogy, Siberian Branch of The Russian Academy of Sciences (RAS) completed radioscopic analysis of the core samples.

The deepest sample they obtained was about 280 years old, which means that the lake was probably even older, because the researchers did not manage to gather samples from the very bottom. So geologically the lake appears young: but not young enough to be a crater lake caused by Tunguska.

'Besides, there are other deep, practically round lakes in the Tunguska reserve, which look like Lake Cheko and probably have the same geological origin,' said a statement from the expedition centre of the Russian Geographical Society in the Siberian Federal District.