Fiery 'airburst' of superheated gas slammed into Antarctica 430,000 years ago
Roughly 430,000 years ago, an incandescent ball of hot gas came barreling out of the sky and slammed into Antarctica — and now, scientists have found tiny bits of debris formed by that impact.
The team scooped up the mineral particles from Walnumfjellet in the Sør Rondane Mountains of Queen Maud Land, Antarctica, which is located south of Africa on the eastern side of the continent. ...
The chemical composition of the particles suggested that they formed hundreds of thousands of years ago during an airburst in the lower atmosphere, which occurs when a meteorite becomes vaporized before hitting the ground, according to the new study, published online March 31 in the journal Science Advances. ...
Next, to estimate when these particles formed, the team went hunting for reports of similar meteorite touchdowns. It turned out that similar particles had been captured in ice cores drawn from other regions of Antarctica, including two summits known as the EPICA Dome C and Dome Fuji. Studies suggest that these meteorites fell to Earth 430,000 and 480,000 years ago, respectively, and by comparing the newfound particles to these other ones, the authors estimated that the Walnumfjellet particles formed 430,000 years ago. ...
Considering the size, shape and density of the particles, the team was also able to produce a "very rough calculation" as to the size of their parent asteroid ... The particles' fused appearance hints that the cloud of hot gas in which they formed was very large and very dense, which allowed the minerals to collide and melt into one another on their way to Earth. This hints that the original asteroid was likely between 328 feet and 492 feet (100 and 150 meters) in diameter. ...
Based on their numerical models, "it turns out that such an asteroid will not reach the ground … basically it would be vaporized into a cloud of superheated meteoritic gas" ... The cloud of gas would then continue descending toward the ground at a similar rate to the original asteroid — "we are talking kilometers per second" ...
"This very dense, incandescent plume that would reach the surface, this is extremely destructive. This could destroy a large city in a matter of seconds, and do severe damage over hundreds of kilometers" ...
Airburst events occur much more frequently than asteroid impacts that create large craters in the crust ...
Tunguska-like events are estimated to occur "once every 100 to 10,000 years, which is orders of magnitude more frequent than large crater-forming impacts" ...
The study suggests "that we should worry more about smaller asteroids, between a few tens of meters and 200 meters [32-656 feet in diameter], than much larger asteroids resulting in impact-cratering events" ...
