The Tunguska event is often described as the biggest impact event in recorded human history.

In the early morning hours of June 30, 1908, something caused a colossal explosion and a shining ball of light in the sky above Siberia, destroying 80 million trees over an area of 800 square miles.

The energy of the blast is estimated to have been equivalent to the explosive force of as much as 15 megatons of TNT. To put it into perspective, that’s about a thousand times more powerful than the atomic bomb dropped on Hiroshima during World War II.

Because of the harsh conditions of the Siberian outback, the first scientific expedition to the impact area would have to wait 19 years. When the team finally made its way there, mysteriously, no impact crater was ever discovered. There were, however, rock fragments that could have been from a meteorite.

In a brand-new Russian study, researchers have suggested a strange alternative to what exactly transpired in the Tunguska event.

They concluded that nothing actually hit the ground at all. Instead, a gigantic iron asteroid flew through the Earth’s atmosphere before heading back out into space. 

“We have studied the conditions of through passage of asteroids with diameters of 200, 100 and 50 meters, consisting of three types of materials—iron, stone and water ice—across the Earth’s atmosphere,” the team wrote.

The researchers said that their findings from studies on other asteroids do support this new theory.  

“The conditions of this passage with a subsequent exit into outer space with the preservation of a substantial fraction of the initial mass have been found,” the team wrote.

“The results obtained support our idea explaining one of the longstanding problems of astronomy—the Tunguska phenomenon, which has not received reasonable and comprehensive interpretations to date.”

Dr. Sergei Karpov, of the Kirensky Physics Institute, said this particular iron-asteroid theory could answer some important questions.

“At present, there are over 100 hypotheses about the nature of the Tunguska phenomenon,” he told The Siberian Times.

“They include the fall of a small asteroid measuring several dozen meters, consisting of typical asteroid materials, either metal or stone, as well as ice. We calculated trajectory characteristics of space from 50 to 200 meters in diameter, and our modeling shows that it could not consist of rock or ice because, in contrast with iron, such bodies fall apart quickly because of colossal aerodynamic pressure in the atmosphere.”

There have been several other theories proposed for the Tunguska event. One cites Nikola Tesla’s experiments with wireless transmission that may have inadvertently caused the explosion. And there is always the speculation that the explosion was caused by a UFO.

Ethen Kim Lieser is a Tech Editor who has held posts at Google, The Korea Herald, Lincoln Journal Star, AsianWeek and Arirang TV. He currently resides in Minneapolis.