Researchers have been studying geological series since the 19th century in order to reconstruct the evolution of flora, fauna and climate over millions of years. Until now, however, almost nothing was known about ancient meteor fluxes – which makes sense since impact is rare and battered celestial bodies quickly decompose when they encounter Earth’s oxygen. A new study published in PNAS shows how Lund researchers reconstructed the meteor bombardment towards Earth over the past 500 million years.

“The research community previously believed that the flow of meteorites to Earth was linked to dramatic events in the asteroid belt. The new study, however, shows that the flow was instead very stable,” says Birger Schmitz, professor. of geology at Lund University.

To conduct the study, researchers at Lund University’s Astrogeobiology Laboratory dissolved nearly ten tons of sedimentary rocks from the ancient seabed in strong acids, as the sediments contain meteorite residue dating from their fall. on earth.

Meteorites contain a small fraction of a mineral, chromium oxide, which is very resistant to degradation. The microscopic grains of chromium oxide have been sieved in the laboratory and serve as time capsules rich in information.

“The dissolved sediments represent 15 periods over the past 500 million years. In total, we have extracted chromium oxide from nearly 10,000 different meteorites. The chemical analyzes then enabled us to determine which types of meteorites the grains represent ”, explains Birger Schmitz.

A few thousand meteorites land on the Earth’s surface each year and around 63,000 space rocks have been documented by science. Space rocks originate from the asteroid belt between Mars and Jupiter where celestial bodies beaten by gigantic collisions revolve around the sun.

“We were very surprised to learn that only one of the 70 largest asteroid collisions that have occurred in the past 500 million years has resulted in an increase in the flow of meteorites to Earth. For some reason. , most of the rocks remain in the asteroid belt, ”says Birger Schmitz.

The study not only disrupts generally accepted theories of meteorite fluxes; it also offers entirely new perspectives on the types of celestial bodies most at risk of colliding with Earth and their origin in the solar system. From the point of view of geologic time, celestial bodies the size of a kilometer regularly collide with the Earth. One of these events took place 66 million years ago, when a celestial body stretching over 10 kilometers struck the Yucatán Peninsula. The impact was part of the reason the Earth turned dark and the dinosaurs starved to death.

“The future impact of even a small asteroid, for example in the sea near a populated area, could have disastrous results. This study provides important insight that we can use to prevent this from happening; for example, by trying to quickly influence the trajectory of the approach of celestial bodies, ”concludes Birger Schmitz.

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