Tiny rock fragments trapped in Antarctic ice reveal the oldest known mid-air explosion of an asteroid, dating back 2.5 million years.
The Earth’s rocky surfaces bear the scars of countless asteroid and comet impacts, evident in the numerous craters dotting our planet. However, some celestial visitors meet a different fate – disintegrating in the atmosphere before reaching the ground. These airbursts, though leaving no crater, can be equally destructive.
A recent study published in Earth and Planetary Science Letters sheds light on such an ancient event. Researchers, led by Dr. Matthias van Ginneken, analyzed over 100 tiny rock fragments (micrometeorites) found within the Antarctic ice. These spheroidal particles, each roughly the width of a human hair, revealed a surprising story.
Chemical analysis identified olivine and spinel as the dominant minerals, suggesting they originated from an ordinary chondrite asteroid. The presence of specific oxygen isotopes further confirmed their formation in an airburst that interacted with ice. This “touchdown” event, as Dr. van Ginneken calls it, would have been particularly devastating, releasing immense heat and pressure upon impact.
This discovery marks the oldest recorded airburst in Earth’s history, pushing back the timeline by millions of years. While only two other such events from 480,000 and 430,000 years ago are documented, experts believe many more lie hidden in the geological record.
“It’s totally believable that events would have occurred in that time period,” says physicist Jason Pearl, highlighting the frequency of smaller asteroid impacts.
Dr. van Ginneken is optimistic about uncovering further evidence. “I’m convinced there are more examples,” he declares, emphasizing the importance of studying these ancient events to understand the impact history of our planet and potential future threats.
This research not only rewrites the timeline of airbursts but also serves as a reminder of the dynamic and potentially destructive nature of our cosmic neighbourhood.