💥 A major object crashed in Brazil 6.3 million years ago

Recently unearthed glass fragments in Brazil testify to a major event that occurred several million years ago.

Called tektites, these fragments form when an object from space strikes the Earth with colossal force, melting the surface rock. The molten material is then ejected into the atmosphere, where it cools rapidly to form this glass. Until now, only five major tektite strewn fields were recognized worldwide, making the Brazilian discovery particularly notable.


Named geraisites after the state of Minas Gerais where they were initially found, these specimens were studied by a team led by Álvaro Penteado Crósta, a geologist at the University of Campinas. The results are detailed in the journal Geology. First identified in three municipalities, the geraisites were later spotted in other states, now covering more than 900 kilometers (about 559 miles), an extent that indicates a large-scale impact.

To the naked eye, these fragments appear black and opaque, but they become translucent and take on a gray-green tint under intense light. Their dark surface is speckled with small cavities, traces of gas bubbles formed during rapid cooling in the atmosphere. These physical characteristics distinguish them from other natural glasses like European moldavites, often used in jewelry.

The dating of these geraisites indicates that the impact occurred approximately 6.3 million years ago, towards the end of the Miocene epoch. Furthermore, chemical analyses show a low water content, typical of tektites, and a silica-rich composition, with fluctuations in trace elements like chromium and nickel. These clues point research towards an ancient source rock, likely located in the São Francisco craton.

No associated crater has been identified yet, a common situation for this type of event. To estimate the energy released and the impact parameters, scientists use mathematical models. This discovery thus fills a gap in the geological history of South America and suggests that tektites might be more widespread than previously thought, sometimes being mistaken for ordinary glass.

How are tektites formed during a cosmic impact?

Tektites appear when objects like asteroids or comets collide with the Earth at high speed. The released energy is so intense that it instantly vaporizes and melts the surface rock. This molten material is ejected high into the atmosphere, where it undergoes rapid cooling within seconds to minutes.

During this aerial trajectory, the droplets of molten rock take on various aerodynamic shapes, like spheres, teardrops, or discs. The speed and angle of impact directly influence the distance traveled and the distribution of fragments on the ground. This process explains why tektites are often scattered over vast areas, forming what are called strewn fields.

The chemical composition of tektites reflects that of the melted terrestrial rock, but with modifications due to the high temperatures. They are generally poor in water, which distinguishes them from volcanic glasses like obsidian. This is an important clue for identifying their extraterrestrial origin, as impacts generate extreme conditions that eliminate moisture.