Rock fragments may indicate the oldest asteroid disintegration in the air
About 2.5 million years ago, an asteroid exploded over Antarctica. This hypothesis is supported by chemical analysis of more than 100 small rock samples left in the ice of the White Continent, the researchers report in the journal Earth and Planetary Science Letters. According to them, this ancient explosion in the air over Antarctica is considered the oldest known.
Researchers analyzed 116 small rock samples found in glaciers on the continent of Antarctica. They discovered minerals characteristic of asteroids, such as olivine and spinel. The exact composition indicates that these rocks were formed by an air explosion. According to scientists, such asteroid airbursts are especially destructive, like a huge torch that vaporizes everything around.
The surface of the Earth and other bodies is often subject to impacts from asteroids, forming noticeable craters. However, sometimes an object disintegrates in the atmosphere before reaching the surface and therefore does not leave a crater. Such air explosions have enormous destructive power, converting kinetic energy into shock waves, pressure and heat.
“All energy is released in the atmosphere in the form of shock waves and thermal radiation,” — say cosmochemist Matthias van Ginneken.
This is exactly what happened in 2013 after an approximately 20-meter asteroid broke apart high above Chelyabinsk. When the resulting shock wave reached the ground, it broke thousands of windows. In 1908, an even more catastrophic explosion in the air occurred over the Tunguska River basin, when a meteorite about three times larger than the Chelyabinsk one disintegrated in the atmosphere and leveled more than 2 thousand square kilometers of forest.
Scientists believe they have found evidence of such an explosion, which occurred between 2.3 and 2.7 million years ago over Antarctica.
«Chemical analysis of microscopic rock fragments collected in Antarctica shows that they correspond to a type of asteroid known as an ordinary chondrite that disintegrated in the atmosphere,” — explain the study's authors.
The Earth is quite often bombarded with large fragments of extraterrestrial material, according to physicist Jason Pearl. He added that meteorites like Chelyabinsk and Tunguska occur approximately every 50 and 500 years, respectively.
Van Ginneken is aiming to find more airbursts in the geological record. According to him, there must be others that can be found.
«I am convinced that there are more examples. It is likely that the events would have occurred during that period of time,” — notes the researcher. New data emerged after a meteorite weighing 7.6 kilograms was found in Antarctica, according to sciencenews.