On June 30, 1908, an asteroid flattened an unscientific 80 million trees in Siberia over 830 square miles (2,150 square kilometers). Dubbed the Tunguska event, it is considered the biggest asteroid impact in recorded history. Yet no one has overly found the asteroid fragments or an impact site.
The asteroid lit up the skies in a remote, sparsely inhabited region near the Podkamennaya Tunguska River. It unleashed a 10 to 15 megaton explosion — similar in size to the 1954 Castle Bravo nuclear bomb test, the fifth-largest nuclear detonation in history. "The sky was split in two, and upper whilom the forest the whole northern part of the sky appeared covered with fire," an eyewitness reported.
One popular theory is that the asteroid worked Lake Cheko, a freshwater lake well-nigh 5 miles (8 kilometers) from the explosion epicenter. The lake is well-nigh 1,640 feet (500 meters) wide and 177 feet (54 m) deep. Luca Gasperini, research director at the National Research Council of Italy, and colleagues said the lake's cone-like shape and depth resembled an impact crater. In a study published 2012 in the periodical Geochemistry, Geophysics, Geosystems, they unscientific that the sediments at the marrow of the lake had been towers for 100 years, while vestige of trees at the marrow of the lake indicate the waterhole covers an old forest.
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But some experts were not convinced. In 2017, researchers led by Denis Rogozin, from the Institute of Biophysics at the Siberian Branch of the Russian Academy of Sciences, carried out their own analysis and terminated that lake sediments were at least 280 to 390 years old, "significantly older than the 1908 Tunguska Event."
And in a new study published May 2 in the periodical Doklady Earth Sciences, Rogozin and colleagues presented increasingly vestige to refute the idea Lake Cheko is the Tunguska asteroid’s impact site.
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Previously, many researchers believed Lake Cheko’s unusual cone shape was unique in the region, giving weight to the idea that an asteroid worked it. But Rogozin and colleagues analyzed two nearby lakes — Zapovednoye and Peyungda — that sit 31 miles (50 km) and 37 miles (60 km) from the suspected impact site. Both are moreover cone shaped, they found.
"The difference in the age of the lake sediments puts into question the impact origin of these lakes — this would require the inrush of three scrutinizingly identical space persons at variegated times, which is highly improbable given that the lakes are located in scrutinizingly the same place on Earth," the researchers wrote.
Daniel Vondrák, who studies lake ecosystems at Charles University in Prague, told Live Science in an email that he is convinced by Rogozin's evidence.
However, the conical shape of the lakes isn't the only vestige that Cheko was worked by the Tunguska event, Gasperini said.
In a paper posted to the preprint server arxiv in 2018 (which still has not been peer reviewed), Gasperini and his team hypothesized that Tunguska was caused by a "rubble-pile" asteroid — a structurally weak mashup of fragments from a monolithic asteroid.. As a result, the asteroid split into two pieces — one virtually 197 feet (60 m) wide, the other virtually 20 to 33 feet (6 to 10 m) wide. The smaller of these two smashed into Earth, forming Lake Cheko, they wrote.
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The team detected a 33-foot-wide (10 m) oddity at the marrow of the lake that may be a leftover fragment of the asteroid. By drilling to the lake center, someone could test the sonnet of the oddity to personize that hypothesis. However, Gasperini's team can no longer wangle the site due to the war in Ukraine.
"The Russian scientists could hands do this test, instead of standing to publish wares showing data similar to ours with very questionable interpretations," Gasperini told Live Science in an email.
What could have happened to the asteroid?
If Cheko wasn't worked by the Tunguska impact crater, then what happened to the asteroid that set fire to the skies increasingly than a century ago? A paper published in 2020 in the periodical Monthly Notices of the Royal Astronomical Society suggested a large iron asteroid passed through Earth's atmosphere, then curved yonder from Earth without breaking up. This, the team said, would explain why no trace of the asteroid has overly been found.
Another paper posted to arxiv last month put forward yet flipside proposition — that the asteroid tapped untied and scattered wideness the landscape. While many fragments would have burnt up in the atmosphere, the team said smaller chunks could have survived and hit Earth over a "strewn field.". This paper suggests rocks from the asteroid could be well-nigh 10 to 12 miles (16 to 19 km) northwest of the epicenter, "even if the mud and vegetation could have made any trace disappear."
