Biggest explosion in documented history is STILL a mystery: New study fails to find cause of 1908 Tunguska blast that 'split the sky in two' and flattened 80 million Siberian trees

The explosion occurred on June 30, 1908 in the Tunguska region of Siberia [CN]

1908年6月30号，西伯利亚通古斯卡地区发生大爆炸。

Eighty million trees flattened in blast, charred reindeer found by hundreds[CN]

8千万颗树在爆炸中被摧倒夷平，上百只驯鹿烧成焦炭。

Eyewitnesses at the time said it was as though the sky was split in two[CN]

当时的目击者宣称天空似乎被劈成两半。

Scientists say it was likely a comet or asteroid, though little evidence found[CN]

科学家宣称可能是彗星或者小行星撞击产生的，尽管证据几乎无迹可寻。

Others have suggested UFOs, supernatural activity, or the curse of a god[CN]

其他人则说有可能是不明飞行物，超自然的现象，或者是上帝的诅咒。

More than 100 years ago, a massive explosion ripped through the sky over the Tunguska region of Siberia, flattening trees nearly 31 miles around. From UFO theories to speculation about the supernatural, the mysterious event has spurred explanations of all kinds[CN]

100多年前，西伯利亚通古斯卡地区，一次大爆炸划破天际，方圆约31英里的树木悉数被撂倒。从不明飞行物到各种超自然力量的揣测，这次谜之事件引发了各种解说。

With no impact crater and little evidence of such an object ever found, scientists remain perplexed as to what truly caused the event in which 'the sky was split in two.' The affected area is pictured in 2008, left, and during an Russian expedition decades earlier[CN]

没有陨石坑，实物也无迹可寻。科学家们仍是疑窦重重，究竟是什么引发了此次爆炸，将天空划分成两半。图片摄于2008年的事发地带（左图），早在几十年前俄国探险队到过此处。

The blast is thought to have been produced by a comet or asteroid hurtling through Earth's atmosphere at over 33,500 miles per hour, resulting in an explosion equal to 185 Hiroshima bombs as pressure and heat rapidly increased[CN]

此次爆炸普遍认为是彗星或小行星以每小时超过33,500英里的速度撞击地球大气层造成的。随着压力和热量的急剧增加，导致了等同于185颗原子弹的大爆炸。

The possibility of an asteroid explosion was first proposed in 1927 by Leonid Kulik, 20 years after the event. A 1938 image from Kulik's investigations is shown above

Eighty million trees had been laid flat in the blast, and the charred carcasses of reindeer were found by the hundreds. The area is shown in 1908, left, and 1938, right, where a tree can be seen with the top half shorn off from the explosion

Numerous studies have attempted to make sense of what happened on June 30, 1908 at Tunguska, a remote region with long, hostile winters and short summers that render the environment an uninhabitable swamp

More than 100 years ago, a massive explosion ripped through the sky over the Tunguska region of Siberia, flattening trees nearly 31 miles around.

The blast is thought to have been produced by a comet or asteroid hurtling through Earth's atmosphere at over 33,500 miles per hour, resulting in an explosion equal to 185 Hiroshima bombs as pressure and heat rapidly increased.

But, with no impact crater and little evidence of such an object ever found, scientists remain perplexed as to what truly caused the event in which 'the sky was split in two' - and a new study has failed to reach a conclusion.

Numerous studies have attempted to make sense of what happened on June 30, 1908 at Tunguska.

This is a remote region with long, hostile winters and short summers that render the environment an uninhabitable swamp, according to BBC.

From UFO theories to speculation about the supernatural, the mysterious event has spurred explanations of all kinds, many of them lacking scientific basis.

Some scientists even suggested a black hole had collided with Earth – but other experts quickly shot down the idea.

On the 100 year anniversary of the explosion, Don Yeomans of Nasa's Near-Earth Object Office at the Jet Propulsion Laboratory explained that the locals believed the event marked the visitation of the god Ogdy, who they feared had cursed the area.

Eighty million trees had been laid flat in the blast, and the charred carcasses of reindeer were found by the hundreds.

In a review published this year in the Annual Review of Earth and Planetary Sciences, Natalia Artemieva of the Planetary Science Institute in Tucson, Arizona explains that the event followed a clear course.

The object likely entered the atmosphere at 9-19 miles per second, and would have been extremely fragile, destroying itself roughly six miles above Earth.

Any remaining traces would be cosmic dust, BBC explains, making them extremely difficult, as they could be just a millimetre in size.

The blast sent shock waves as far away as England, and even people in Asia saw the sky glowing until midnight – bright enough to read a newspaper outdoors.

'Suddenly in the north sky…the sky was split in two, and high above the forest the whole northern part of the sky appeared covered with fire,' recalled an eyewitness, who was thrown from his chair by the heat blast 40 miles from the site of the explosion.

'At that moment there was a bang in the sky and a mighty crash…The crash was followed by a noise like stones falling from the sky, or of guns firing. The earth trembled.'

The possibility of an asteroid explosion was first proposed in 1927 by Leonid Kulik, 20 years after the event.

Others suggested the space-object may instead have been a comet, made up of ice rather than rock, meaning it would have evaporated as it entered Earth's atmosphere.

Later investigations revealed small traces of silicate and magnetite in the soil, which were found to be high in nickel.

This analysis pointed toward the explanation of a meteoroid of asteroid origin, according to BBC, which annihilated itself as it plunged through Earth's atmosphere.

More recent studies, including one in 2013, confirm that rock samples found in the area are in fact of meteoric origin with traces of a carbon mineral called lonsdaleite, which is known to form when meteorites crash into Earth.

But, some scientists warn that these findings do not definitively explain the bizarre explosion – with meteor showers being a frequent occurrence, these samples could be the remnants of a much smaller, unnoticed event.

In 2007, a team of Italian scientists proposed that Siberia's Lake Cheko is actually the impact crater from the object, as it was not on any maps prior to this event.

This explanation, too, is unpopular among scientists,  Artemieva explained to BBC, as the lake is shallow enough to recover any remnants that would exist.

To some degree, the Tunguska event still remains a mystery, which scientists are continually working to solve – but, whether it be from a comet or asteroid, most agree that the explosion was caused by a large cosmic body slamming into Earth's atmosphere.