Since the 19th century, researchers have studied geological sequences in order to reconstruct how wildlife, plants and climate have changed over millions of years. But so far almost nothing is known about the ancient meteorite flow. This is not strange. Rain is rare and shredded orbs quickly endure contact with Earth’s oxygen. But in a new study published in the scientific journal PNAS, researchers in Lund have succeeded in reconstructing what meteorite bombardments of Earth looked like during the past 500 million years.
Stable flow of meteorites
The research scientist previously believed that the meteorite flow towards Earth was associated with dramatic events in the asteroid belt. But our new study shows that the flow was instead very stable, says Berger Schmitz, a professor of geology at Lund University.
For the study, researchers at the university’s Astrobiology Laboratory dissolved nearly ten tons of sedimentary rock from ancient seabeds in strong acids. The reason for this is that the sediments contain remnants of meteorites that eventually fell to Earth. Meteorites contain a small portion of a metal, chromium oxide, which is highly weatherproof. The microscopic chromium oxide grains, which are examined in the laboratory, act as a kind of time capsule and carry a lot of information.
The sediments that we have melted represent 15 time periods over the past 500 million years. In total, we extracted chromium oxide grains that originated from about 10,000 different meteorites. Through chemical analyses, we were then able to determine what types of meteorites the grains represented, says Berger Schmitz.
Most of the rocks remain in the asteroid belt
Every year, a few thousand meteorites land on the surface of the Earth. In total, about 63,000 space rocks have been documented by science. These originate from the asteroid belt between Mars and Jupiter, where celestial bodies shredded from giant collisions orbit the Sun.
We were very surprised to see that only one in 70 major asteroid collisions in the past 500 million years has resulted in an increased flow of meteorites to Earth. For some reason, says Berger Schmitz, most of the rocks remain in the asteroid belt.
Prevent future collisions
The study does not only put an end to accepted meteor flow theories. It also provides entirely new perspectives on the type of celestial bodies most at risk of colliding with Earth, and their place in the Solar System. From a geological time perspective, kilometers of celestial bodies regularly collide with the Earth. Something happened, among other things, 66 million years ago when a ten kilometer celestial body crashed into the Yucatan Peninsula and contributed to the darkening of the Earth and the starvation of the dinosaurs.
Any future impact of even a smaller asteroid near a populated area could lead to a catastrophe with millions of deaths. This study gives us important knowledge that we can use to prevent this from happening, for example by trying to influence the orbits of emerging celestial bodies, says Berger Schmitz.
Asteroids crash and meteorites delivered to Earth during the past 500 million years, Friedrich Tervelt and Berger Schmitz), Proceedings of the National Academy of Sciences, PNAS.
Berger Schmitz, Professor of Geology in the Department of Physics, Lund University, [email protected]
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