SCIENCE LAB SPECIAL : ANCIENT EVENT

A forgotten cosmic impact was hidden in a museum's glass shards : Every few million years, a sizable asteroid slams into our planet.

Researchers have now found evidence of such a cataclysm roughly 11 million years ago, thanks to shards from a more recent Earthly encounter with a giant space rock.

The scientists described their discovery in a new paper. Thousands of pieces of black glass are stored in a collection at the South Australian Museum in Adelaide.

They are tektites, which sometimes form when terrestrial rocks melt in the intense heat and pressure of an asteroid impact.

Researchers long believed that the museum's tektites came from an impact that occurred 800,000 years ago.

That event scattered tektites across 100 percent of Earth's surface. These objects are named Australasites, and they are the most common of all known tektites.

In 1969, two scientists reported the discovery of eight Australasites with an odd chemical composition. Follow-up work suggested that those chemical outliers were at least two million years old.

In 2023, researchers from Aix-Marseille University in France led by Anna Musolino, a geoscientist, traveled to the Adelaide museum and started by dunking more than 5,000 Australasites in liquid to estimate their density. 

The researchers kept tektites that sank and were therefore very dense, and also retained tektites with high levels of iron.

They brought 417 tektites to France for further analysis. In the end, six tektites stood out as being chemically perplexing.

And when the team age-dated two of those oddballs, they recovered an age of 10.8 million years.

The World Students Society thanks Katherine Kornei.