Glassy Beads Hint of a Mysterious Missing Crater

Experts have found a ‘breadcrumb trail’ of debris from an 800,000-year-old meteor impact. (Image: via pixabay / CC0 1.0)

Imperial experts have found a “breadcrumb trail” of glassy beads debris from an 800,000-year-old meteor impact. Around 800,000 years ago, a 20 kilometer meteor collided with the Earth, producing a zone of glassy beads debris in Australasia that covers a tenth of the Earth’s surface.

However, despite the impact’s relatively young age in geological terms, and the meteor’s size, the resulting crater’s location eludes us. Earth scientists Dr. Matthew Genge, from Imperial College London, and Dr. Matthias Van Ginneken, from Vrije University in Belgium, are on a mission to find the impact site.

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Dr. Genge, from Imperial’s Department of Earth Science and Engineering, said:

Cosmic glassy beads crumb trail

Scientists have already found debris from the collision in the form of glassy “beads” a centimeter in diameter known as tektites, scattered from Australia to Vietnam. The tektites are thought to begin as molten spray from the impact, and have settled over an area of more than 150 million square kilometers.

Following impact debris could help experts find mysterious crater. (Credit: Imperial College London)
Following impact debris could help experts find mysterious crater. (Credit: Imperial College London)

Now, Dr. Genge and Dr. Van Ginneken have found smaller versions of the glassy beads from the same impact, called microtektites, as far south as Antarctica. They uncovered the tiny round structures, which are the width of a human hair, in the Larkman Nunatak in Antarctica’s Grosvenor Mountains. Dr. Genge said:

Glassy beads from Larkman Nunatak.
A microtektite from Larkman Nunatak. It is the width of a human hair. (Credit: Imperial College London)


During and after an impact, levels of potassium and sodium in the resulting debris drop as they travel. The hottest debris ends up farthest away, and ends up carrying lower levels of potassium and sodium, which provides a “fossil compass” that points to the area of impact.

Larkman Nunatak. Arrow indicates where the microtektites were collected. (Credit: Imperial College London)
Larkman Nunatak. Arrow indicates where the microtektites were collected. (Credit: Imperial College London)

Dr. Matthew Genge, Department of Earth Science and Engineering, said:

Dr. Van Ginneken explained:

Finding hotter debris furthest from the collision site seems counter-intuitive, but Dr. Genge says this effect is to be expected:

Collision course

Meteors crash into Earth more often than you might think. Despite their sometimes catastrophic effects, their remains can be difficult to detect. Yet the experts’ discovery has more significance than just one mysterious impact years ago — it might help them find other missing craters.

The sampling area at Larkman Nunatak. (Credit: Imperial College London)
The sampling area at Larkman Nunatak. (Credit: Imperial College London)

Dr. Genge and Dr. Van Ginneken believe their technique of testing levels of potassium and sodium among tektites and microtektites could help them trace more ancient impacts. Dr. Genge said:

Nonetheless, they say this is the best evidence yet that the collision occurred 800,000 years ago — but the ultimate proof lies in finding the crater itself. The team hopes these tiny new clues will help lead the way.

Provided by: Imperial College London  [Note: Materials may be edited for content and length.]

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