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March 31 (UPI) -- Tiny meteorite particles found in the mountains of Antarctica suggest the Southern Continent's ice sheet was singed by an asteroid touchdown event some 430,000 years ago, according to a new paper published Wednesday in the journal Science Advances. The spherules were discovered several years ago by a team of Belgian and British scientists hunting for micrometeorites in sediment deposits on the peaks of the Sør Rondane Mountains of East Antarctica.
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"It did not take much time for them to find micrometeorites and very unusual looking particles, which looked like several spherules fused together at very high temperature," Matthias van Ginneken told UPI in an email.
"Knowing that these were not micrometeorites but still most likely extraterrestrial, the idea of them resulting from a large meteoritic event seemed a strong probability," said Ginneken, a planetary scientist and researcher at the University of Kent.
Not all asteroid impacts produce craters. Some are vaporized just before reaching Earth's surface, triggering an atmospheric explosion. These events are called airbursts.
Another type of impact, a touchdown event, shares characteristics with both cratering events and airbursts.
"[A touchdown event] is an airburst so large that the extremely hot cloud of meteoritic gas resulting from the vaporization and explosion of the asteroid will not have time to lose momentum before reaching ground level," Ginneken said.
"Thus, this jet of gas will reach ground level at hypervelocity, resulting in an interaction of the meteoritic material with ground material, while a crater will not form as there is no solid impactor left to do so," Ginneken said.
Back in the warmth of their labs at Princess Elisabeth Antarctica, the Belgian research station, scientists identified the particles as condensation spherules, or chondrites, produced by a meteoritic event.
Researchers later returned to the Antarctic summits to collect more samples and map the distribution of spherules in the Sør Rondane Mountains.
Using the distribution and concentration of meteoritic particles as a guide, scientists estimated the touchdown event was produced by an asteroid roughly measuring between 350 and 400 feet in diameter.
To date the impact, researchers successfully paired the glassy spherules with particles found in disparate ice cores that contained evidence -- a layer of extraterrestrial dust -- of a 430,000-old meteoritic event.
"This research is significant as it will serve as a guide to look for similar touchdown impacts in the geological record, allowing us to improve our knowledge of the impact history of Earth," Ginneken said.
"A more complete impact record would allow us to better constrain the flux of large asteroids to Earth, as it is complementary to direct observations and numerical modeling of this flux. It will also help us reassess the threat posed by such touchdown impacts and the effects at the region scale these could have," Ginneken said.
Researchers said they plan to continue studying the condensation spherules using an array of analysis techniques, including isotopic analysis.
They know the size and the timing of the asteroid, but Ginneken and his research partners hope to pin down the asteroid's composition.
"We know it was most likely an asteroid linked to carbonaceous chondrites," he said.
"Knowing the group of carbonaceous chondrite would allow us to better define the potential physical properties of the impactor and, thus, improve the numerical models of this touchdown impact," Ginneken said.
