Where did the Chicxulub crater disappear

Impact crater of a huge asteroid discovered in Laos

Vientiane - A massive asteroid hit Earth 790,000 years ago. Scientists found clues for this in many places on our planet in the form of so-called tektites, also known as rock glasses. These vitreous bodies, up to a few centimeters in size, are scattered over about a tenth of the earth's surface, including Australia, Southeast Asia and the Antarctic.

So far, however, it was unclear where exactly the chunk fell from space. Despite an intensive search in the past decades, the crater was not found, reports an international team led by Kerry Sieh from the Earth Observatory of Singapore in the "Proceedings" of the US National Academy of Sciences ("PNAS"). "This suggests that either there never was a crater or that it has disappeared - through erosion or by being buried," explains Sieh.

But now the scientists found what they were looking for: They discovered the long-sought crater on the Bolaven Plateau in the south of Laos. There is a large field of basalt rock that must have been created by volcanism. According to the researchers, the impact crater is buried under this thick layer. The group supports their thesis with several pieces of evidence.

17 by 13 kilometers large crater

Certain rock on the plateau fits on the one hand geochemically to the previously discovered tektites. According to analyzes, the lava flows over and near the suspected crater did not flow until after the impact. And finally, the scientists found so-called gravity anomalies in the ground, which suggest a 17 by 13 kilometer crater. A few kilometers away from the suspected crater there are boulders that the researchers say were probably ejected when the meteorite hit.

The exact age of the tektites was determined almost four years ago by researchers working with the Heidelberg geoscientist Mario Trieloff. The group had not only examined tektites from the Asia-Australian region - which Sieh's work is about - but also those from Canada and Belize (Central America).

Second impact

In doing so, they came to the conclusion in the journal "Geochimica et Cosmochimica Acta" that there must have been at least one further impact around 790,000 years ago. This is because the vitreous bodies examined all came into being at roughly the same time. However, a different chemical composition of the glass objects from Belize indicates that they were created during a different impact. (red, APA, 2.1.2020)