Some 780,000 years ago, a colossal space rock smashed into Earth. Scientists have known about this Earth-shaking event for some time thanks to strange glass debris that’s strewn across Australia and Asia. However, curiously enough, no one has ever found the impact crater – perhaps until now.
An international team of researchers believes they have found the location of the mysterious crater buried beneath a lava bed in Laos, according to a new study in the journal Proceedings of the National Academy of Sciences.
One of the main clues that led to the possible impact site was the glass blobs, known as tektites, that were kicked out by the meteorite blasting into the ground. Researchers have documented numerous types of tektites, linking them back to the original impact crater. For example, tektites found in North America most likely originated from the impact that formed the Chesapeake Bay crater in Virginia.
However, no one has ever been able to trace the source of tektites found across a large part of Earth’s Eastern Hemisphere, an area referred to as the Australasian strewnfield. Considering the size of the strewnfield – stretching from southern China to southern Australia and across much of the Indian Ocean – the meteorite must have been a big impact.
First up, the distribution of tektites suggests the impact hit somewhere in Southeast Asia. Following up on this lead, a string of analyses on the tektites revealed they had a chemical make-up that links them to the geology of Bolaven volcanic field in Southern Laos. They also discovered unusual sandstone and mudstone boulders less than 20 kilometers (12 miles) away from the Bolaven volcanic field, which could suggest a nearby meteorite impact. Furthermore, gravity measurements of the volcanic field also detected an unusual anomaly, which could be explained by the presence of a vast crater beneath the Earth's surface.
Altogether, their calculations are consistent with a hidden impact crater, measuring around 13 kilometers (8 miles) by 17 kilometers (10.5 miles) wide, lurking beneath the Bolaven volcanic field.
"There have been many, many attempts to find the impact site and many suggestions, ranging from northern Cambodia to central Laos, and even southern China, and from eastern Thailand to offshore Vietnam," Professor Kerry Sieh, study author and principal investigator with the Earth Observatory of Singapore, told CNN.
"But our study is the first to put together so many lines of evidence, ranging from the chemical nature of the tektites to their physical characteristics, and from gravity measurements to measurements of the age of lavas that could bury the crater."
Although backed up by some sturdy evidence, this remains speculative at the moment. After all, the crater is now hidden beneath masses of volcanic rock produced by a lava flow many millennia ago. To confirm their theory, the team must dig deep into the lava field and its geology.