A team of Belgian researchers has found new evidence that a large asteroid exploded just above Antarctica’s ice sheet about 430,000 years ago. The proof lies in small particles with a unique composition found by a Belgian expedition in Queen Maud Land in Antarctica.
Antarctica’s dry, cold climate makes it the perfect place to look for meteorites, geologist Matthias van Ginneken said in an interview with science portal ‘Live Science’. The team found the mineral particles in the Sør Rondane Mountains, Queen Maud Land, which is part of East Antarctica. Ginneken specializes in the study of micrometeorites, or extremely small meteorites the size of dust particles.
“It was my first Antarctic expedition and we found this ideal area to sample on a mountain in Sør Rondane,” said Van Ginneken, who is now researching at the University of Kent in the UK.
After Van Ginneken collected sediment from the summit, he scanned the samples with an electron microscope. The extraterrestrial particles found are called spherical condensed particles. The 17 dark black particles collected by Ginneken are all smaller than 1 millimeter. They were found during the BELAM (Belgian Antarctic Meteorites) expedition 2017-2018, organized by the Belgian station “Princess Elisabeth Antarctica” with funding from the Federal Science Policy (BELSPO).
Exploded in mid-air
Since the asteroid had already exploded in the air, it had left no characteristic impact crater in the ice. It was found that the samples contained so-called beads. When an asteroid explodes in the atmosphere, a large cloud of vaporized and molten rock is formed. The cooling process produces spherical particles – beads – which are deposited on the ice. As a result, the team knew immediately that the material was of foreign origin. It is believed that the asteroid was about 100 by 150 meters.
To estimate when these particles formed, the team set out to find reports of similar meteorite touchdowns. It turns out that similar particles have been found in ice cores from other regions of Antarctica, including two areas known as EPICA Dome C and Dome Fuji. Studies suggest that these meteorites fell to Earth 430,000 and 480,000 years ago, respectively. By comparing the newly discovered particles with the other particles, the authors estimated that the Walnumfjellet particles formed 430,000 years ago.
An asteroid exploded over Chelyabinsk in 2013
Explosions like this are rare. An asteroid had entered the Earth’s atmosphere near the Russian city of Chelyabinsk at about 9:20 a.m. local time on February 15, 2013, and exploded while still in the air.
The shockwave from the asteroid damaged more than 7,000 buildings and injured more than 1,000 people. The shock wave broke windows 58 miles away.
The meteor was observed and filmed many times. It was the largest known meteor in over 100 years. An even larger meteor may have last entered the Earth’s atmosphere during the Tunguska event in 1908.
Heiner Kubny, PolarJournal
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