An international team of researchers led by scientist Elizaveta Kovaleva, from the University of the Western Cape, in South Africa, has shown that mysterious yellow glass fragments First identified 90 years ago in the Libyan desert, they are the product of the impact of a meteorite on Earth. In this way, determining the extraterrestrial origin of this glass culminates a long controversy among the scientific community.

Together with colleagues from universities and scientific centers in Germany, Egypt and Morocco, Kovaleva summarized the findings in a new study, recently published in the journal American Mineralogist. The strange crystals were first described in a scientific article from 1933, and are known as Libyan desert glass.

With unique features

Although natural glass They can be found in different parts of the Earth, such as the moldavites from the Ries crater in Europe or the tektites of the Ivory Coast, none of these examples are as rich in silica as the yellow crystals from the Libyan desert. Furthermore, no pieces or fragments of those dimensions have been found in other places.

As Kovaleva explains in a article published in The Conversation, the Great Sand Sea Desert It extends over an area of ​​72,000 square kilometers linking Egypt and Libya. In some sectors of this endless desert, it is possible to find pieces of yellow glass scattered across the sandy landscape with the naked eye.

The origin of this glass has been the subject of scientific debate for almost a century. Some theories indicate that it could come from volcanoes on the Moon. Other specialists propose that it is the product of a lightning strike, in a process called fulgurites: glass that is formed from the fusion of sand and earth in the sector struck by lightning.

Meanwhile, other hypotheses postulate that these crystals are the result of sedimentary or hydrothermal processes, generated by a massive explosion of a meteorite in the air, or that they come from the crater of a nearby meteorite. In 1996, scientists determined that glass had about 29 million years. They later suggested that the original material was composed of quartz grains, coated with a mixture of clay minerals and oxides of iron and titanium.

Extraterrestrial origin

Now, the team led by Kovaleva analyzed two pieces of yellow glass collected in the Al Jaouf region, in southeastern Libya. When studying the samples with a technique of transmission electron microscopy (TEM) of the latest generation, which allows us to see particles 20,000 times smaller than the thickness of a sheet of paper, specialists found different types of zirconium oxide (ZrO₂) in the crystals.

For these elements to be identified on our planet, it is necessary to achieve pressure and temperature conditions that can only be obtained in the Earth’s crust through the impact of a meteorite, or through the explosion of an atomic bomb. By ruling out the second option, the scientists confirmed the extraterrestrial origin of the yellow crystal of Libya: it would come from the remains expelled from the crater that caused the meteorite upon impact with the Earth.

However, there are still different unknowns to solve in future studies: for example, scientists did not find in the vicinity of the sites where these crystals are seen any impact crater with the location and dimensions to produce the extraterrestrial glass. Although this is a great new mystery, specialists believe that the crater may be close to that area, but remains hidden as it has been eroded and covered in sand.

Reference

Libyan Desert Glass: New evidence for an extremely high-pressure-temperature impact event from nanostructural study. Elizaveta Kovaleva et al. American Mineralogist (2023). DOI:https://doi.org/10.2138/am-2022-8759