Russian Scientists Propose New Hypothesis on the Impact of the Tunguska Meteorite

On June 30, 1908, a massive aerial explosion occurred near the Podkamennaya Tunguska River in what is now the Krasnoyarsk Krai area of Russia, putting that location on the map both literally and physically, as the news of the explosion spread around the world because it also left a wide path of destruction on the ground in the form of an estimated 80 million trees over an area of 830 square miles (2,150 square km) flattened. A large chunk of it may have survived the explosion and crashed into the ground so hard that it formed a crater which eventually became known as Lake Cheko, which is also near the Podkamennaya Tunguska River. Since the area is sparsely populated and the meteor explosion’s aftermath so destructive, the speculation that Lake Cheko was also part of the Tunguska incident has moved ever closer to fact. Siberian scientists have recently spent a lot of time in the area of Lake Cheko trying to prove or disprove the theory. The study was published recently in the journal Doklady Earth Sciences. Place your bets. Was Lake Cheko formed by the Tunguska meteorite?

“According to some estimates, the explosion power was 10 - 40 megatons in TNT equivalent, which corresponds to the energy of an average hydrogen bomb, according to others - 10 - 15 megatons. The exact cause of what happened to this day remains a mystery. Most scientists were inclined to the version of the fall of a meteorite or meteoroid, presumably of cometary origin, or part of a collapsed cosmic body. Lake Cheko is located 8 km from the alleged epicenter of the explosion, so some researchers considered it as a trace of the fall of the Tunguska meteorite.”

The Russian web site Interfax-russia.ru lays out the logic used by scientists to speculate that Lake Cheko was formed by the Tunguska meteorite. The massive explosion was unlike anything people alive at the time had ever seen or heard – remember, this was nearly 40 years before the first atomic bombs were dropped on Japan during World War II. The object was estimated to have exploded at an altitude of 3 to 6 miles (5 to 10 km) and was classified as an impact event because of the wide swath of destruction it left in the Tunguska region. A few eyewitnesses saw the blast in the sky but no one reported an impact. Because of the remoteness of the location, just a few photographs were taken of the destruction. Because of the political situation in Russia at the time, few if any major scientific investigations were undertaken. The Soviet Union also restricted investigations, and those that did take place focused on studying the ground for remnants of the object that could determine exactly what it was (asteroid or comet) and whether it was demolished, skimmed off the atmosphere and back into space, or made any sort of impact.

It wasn’t until 2007 that scientists from the University of Bologna found the small (500 meter (1,600 ft) long, 300 meters (980 ft) wide and 50 meters (160 ft) deep) Lake Cheko and proposed the hypothesis that it was formed by the Tunguska object or a large piece of it. Some researchers found evidence suggesting Lake Cheko was only 100 years old, making it the right age to be Tunguska-caused. That evidence included a relatively thin layer of sediment on the bottom and acoustic-echo soundings showing the shape of lake’s bottom – a cone that could have been caused by an impact. There was even a magnetic reading showing what might be a meter-sized chunk of rock at the very bottom of the cone that could be a meteorite fragment. All of this supported the idea that Lake Cheko was Tunguska-made. Yet this new study says it wasn’t. However, the evidence found was in in the lake … it was around it.

“It used to be that the unusual shape of Lake Cheko was unique for the Tunguska region. This fact was one of the main arguments in favor of its impact origin.”

Scientists from Krasnoyarsk, Novosibirsk and Kazan, including specialists from the Krasnoyarsk Scientific Center of the Siberian Branch of the Russian Academy of Sciences, went to the Lake Cheko area and found two other lakes – Lake Zapovednoe and Lake Peyungda. Both are located in the Tunguska State Nature Reserve and very near to the alleged epicenter of the Tunguska event and Lake Cheko.

described the morphology of the bottom and bottom sediments of lakes Zapovednoe and Peyungda, located on the territory of the Tunguska State Nature Reserve, not far from the alleged epicenter of the Tunguska event. The researchers compared the data obtained with Lake Cheko and questioned the hypothesis of its connection with the Tunguska phenomenon. These two lakes were very similar to each other in shape, size and depth, which suggested they had been formed together. Radiocarbon analysis of bottom sediments from the two lakes showed that Lake Zapovednoye is more than 2 thousand years old and Peyungde is several thousand years old. That means they pre-date the Tunguska event. If Lake Cheko is the result of an impact, it should be very different than these lakes, which were formed by the Tunguska river. When they compared them to Cheko, this is what they found:

“They are similar in shape and size to Cheko Lake, which, according to some researchers, is a trace of the fall of a celestial body as a result of the Tunguska Event. Previously, the unusual shape of Cheko Lake was assumed to be unique to the area. This fact was one of the main arguments in favor of its impact origin. With the example of Zapovednoye and Peyungda lakes, we showed that the shape of Cheko Lake is not unique to this area; the age of the bottom sediments of Zapovednoye and Peyungda lakes exceeds several thousand years. The similarity of the shape of these three lakes and their location in river channels indicate their common origin and testify against the hypothesis about the impact origin of Cheko Lake as a result of the Tunguska Event of 1908.”

The study determined that Lake Cheko was formed by the river at least 300 years ago – well before 1908 and the meteorite. That eliminates it as the final resting place for the last of the Tunguska object. It also lends credence to another recent hypothesis – that the object was not an icy comet or a rocky meteor but an iron asteroid with a size of about 100 to 200 meters (328 to 656 feet) which passed through the Earth's atmosphere at an altitude of 10 - 15 km (6.2 to 9.3 miles), caused the Tunguska shock wave of destruction, then continued on its near-solar orbit with about half of its initial mass intact.

While we still don’t have a positive identity of the space rock that caused the Tunguska event, this new study conclusively proves that Lake Cheko is just a nice little icy Siberian lake.