Scientists study the meteorite that hit the earth 500 million years ago and have a surprise discovery

In the past 500 million years, meteorite showers from space to our planet may not have fallen as we thought.

After analyzing 8,484 kilograms (18,704 pounds) of sedimentary rock from the ancient seabed, the scientists found that major collisions in the asteroid belt did not make any significant contribution to the number of meteorite impacts on Earth, as theorized.

Scientists say the discovery could help protect Earth from asteroid strikes in the future.

"The research community previously believed that the flux of meteorites to Earth was associated with dramatic events in the asteroid belt," said Birger Schmitz, a geologist at Lund University in Sweden. "However, the new study shows that the flux is rather stable. ."

Tracking Earth's meteorite history isn't easy. Impact events involving craters formed by meteorites leaving large objects are rare; many space rocks break apart as they enter the atmosphere, leaving only fragments that fall to Earth.

These fragments are exactly what Schmitz and his colleagues have been looking for: tiny fragments of micrometeorites, preserved in sedimentary layers of the Earth's crust.

They extracted thousands of kilograms of limestone from ancient seabeds in China, Russia and Sweden, representing 15 different periods of the Phanerozoic Era.

These limestone chunks are then dissolved in acid, a technique that extracts chromium spinel — tiny fragments of chromium oxide, a degradation-resistant mineral found in meteorites.

"In total, we extracted chromium oxide from nearly 10,000 different meteorites," Schmitz said, "and then chemical analysis allowed us to determine which type of meteorite the particles represented."

Fascinatingly, their results show stable fluxes, composed mostly of chondrite (stony non-metallic) meteorites, similar to today's fluxes. A notable exception is the increase in this type of meteorites 466 million years ago, associated with the rupture of the parent body of L-type chondrites, which are very low-iron meteorites.

During this period, the meteorite flux increased by a factor of 300, with 99% of the grains coming from this parent body, tapering off after about 40 million years but never completely stopping. Even today, about a third of all meteorites that fall to Earth come from this parent body. This suggests that asteroids leaving the asteroid belt between Mars and Jupiter appear to have come from a very small region.

"We were very surprised to find that only one of the 70 largest asteroid collisions in the past 500 million years resulted in an increase in the flow of meteorites to Earth," Schmitz said. Rocks are left in the asteroid belt."

We're not sure what the cause is yet, but it could help us understand what types of objects might collide with Earth, and where they came from. This is, of course, assuming the team's findings are validated; as they note in their paper, the sampling may not have been comprehensive.

There was no chrome spinel data for 190 million years from the Carboniferous to the early Jurassic, and we know of an asteroid breakup that affected Earth during that time. A family of asteroids that emerged during the Cretaceous -- the period when the team sampled most intensively -- also showed no significant increase in flux from this meteorite.

Future research may help explain the reasons behind these differences. For now, this research represents a new way of understanding the history of Earth's meteorite impacts, and what we can expect from the future.

"Even in oceans close to populated areas, a future impact of even an asteroid could have catastrophic consequences," Schmitz said. "This study provides important understanding that we can use to prevent this This happens; for example, by trying to influence the trajectory of a rapidly approaching celestial body."