Antarctica was blown up by a powerful ‘Airburst’ event 430,000 years ago

Asteroids crashing directly onto Earth’s surface can cause significant damage, but, as new evidence uncovered in eastern Antarctica suggests, asteroids exploding at the entrance can be just as devastating.

Tiny black balls made from igneous rock are evidence of a calamitous event in Antarctica’s Sør Rondane Mountains around 430,000 years ago, according to research published today in Science Advances. An object measuring somewhere 330 to 490 feet (100 to 150 meters) wide entered our planet’s atmosphere, but instead of crashing to the surface and forming a crater, the object exploded before to reach the ground.

Now, that may sound like a good thing, but as geochemist and planetary Matthias van Ginneken pointed out in an email, this “air explosion” event still managed to ravage the icy surface of Antarctica.

When the object exploded, it produced a “superheated gas cloud” resulting from the “vaporization of the asteroid upon entering the atmosphere,” explained van Ginneken, lead author of the study and associate. research at the University of Kent in the United States. Kingdom. This cloud, filled with tiny molten particles and scorching steam, traveled like a jet and at hypervelocity speeds, because “it didn’t have time to lose momentum when it reached the Antarctic ice cap”, did he declare. When this jet reached the surface, it was still moving at speeds approaching several miles per second.

No crater formed as a result of this event, but the contact zone – the region that came into contact with the cloud of superheated gas – was thrown into a landscape of hell, as temperatures soared to several thousands of degrees Fahrenheit.

“This means that anything directly under it would have been vaporized,” van Ginneken explained. “On top of that, a huge shock wave resulted from the explosion of the asteroid near the ground,” he said, adding that if a similar event were to occur in an inhabited area today, “It would be disastrous and extremely destructive for several hundred. of kilometers. “

Indeed, we tend to think of asteroids as posing threats only if they reach the surface, but this ancient event in Antarctica is a chilling reminder of the catastrophic potential of aerial explosions. As van Ginneken pointed out, “Air blasts are a danger that should not be ignored, primarily because they are much more frequent than crater-forming impacts resulting from much larger asteroids.”

We know of at least two aerial events in recent history, both significantly weaker than the one recently documented in Antarctica. The famous Tunguska event of 1908 is the most notable example, in which an explosive asteroid flattened tens of millions of trees across 2,150 square kilometers of Siberia. In 2013, a asteroid exploded over Chelyabinsk, Russia, scaring the population and smashing windows over a large area.

That said, scientists have struggled to identify other historical examples of these calamitous events due to the lack of visible evidence, namely discernible impact craters. The challenge is to locate the remains of the aerial explosions in the geological records.

The search for this elusive evidence led van Ginneken, with co-author Steven Goderis from Vrije Universiteit Brussel and Alain Hubert from Princess Elisabeth Antarctic Station, to the Sør Rondane Mountains of Antarctica. The trio were members of the 2017-2018 Belgian Antarctic Meteorite Expedition, which was funded by the Belgian Federal Office for Science Policy and organized for the explicit purpose of chasing micrometeorites. Most of this research took place when van Ginneken was working at the Royal Belgian Institute of Natural Sciences at the Vrije Universiteit Brussel and at the Free University of Brussels.

The team spent an entire day atop Walnumfjellet Mountain, where they collected glacial sediment from an old, glacier-eroded surface. Back at the station, “it didn’t take long for us to find very unusual-looking micrometeorites and particles that looked like several spherules fused together at very high temperatures,” van Ginneken said, to which he added: “Knowing that they were not micrometeorites but still very likely extraterrestrials, the idea that they were the result of a large meteoric event seemed a high probability.

In total, the scientists found 17 black spherical igneous particles. Using microscopes and laser techniques, they discovered that the particles were between 100 and 300 microns wide and were made up of olivine and iron spinel minerals, fused together by small pieces of glass. But what made scientists understand that these particles were foreign was their chondritic bulk composition and high nickel content. Indeed, “chondrites are primitive meteorites and are the most common type of meteorite falling on Earth,” van Ginneken explained.

To date the particles, the team paired them with other impact particles previously found in the Antarctic ice cores EPICA Dome C and Dome Fuji, in which a large “meteorite event was recorded as a thin layer of dust. alien, ”van Ginneken said. These particles, all dating from the same period, appear to have formed from a single event about 430,000 years ago.

The new research is important in that it demonstrates a way to search the geological records for meteorological weather explosions. But it also serves as a reminder of the threat posed by such events. If something like this happened today in a big city, it would kill millions of people., according to van Ginneken.

All the reasons to continue to search Earth for signs of previous air explosions, while scanning the skies for potential threats.