In the academic journal Earth and Planetary Science Letterspublish“Over tens of millions of years, material from this ring gradually fell to Earth, causing the surge in meteorite impacts seen in the geological record,” said Andy Tomkins, a professor in the School of Earth, Atmospheric and Environmental Sciences at Monash University in Australia and lead author of the study.pointing outis doing.
Impact crater
Reconstructing plate tectonics from this period, known as the Ordovician Period (488 million to 444 million years ago), the team found that all 21 asteroid impact craters that formed during this time period were located within 30 degrees of latitude of the equator at the time — even though more than 70 percent of the continental crust at that time was outside this region, at higher latitudes.
“What’s more, we found that the sedimentary rocks from this period contain a very large amount of meteorite debris,” Tomkins says. The Ordovician period was a time when meteorites frequently bombarded Earth.
Close Encounters
The team believes that these frequent asteroid impacts are caused by large objects approaching Earth, and that the meteorite fragments are the product of these collisions. The reason this happens is due to the “Roche limit” (the closest an object can get to another object before being destroyed by tidal forces), which for Earth is about 20,000 km. Once a large object gets within this distance, it can break up due to gravitational forces (tidal forces).
This resulted in a ring of debris surrounding Earth, similar to the rings around Saturn today, which triggered showers of debris that rained down on the planet’s surface over tens of millions of years, coinciding with a surge in meteorite impacts preserved in the geological record, the team says.
Shadow of the Ring
The debris ring cast a dark shadow over Earth, potentially affecting global climate. The End-Ordovician glacial period is considered one of the coldest periods in Earth’s history over the past 500 million years, bringing with it cold temperatures, glaciers, and a significant drop in sea levels.
If rings in the Earth were responsible for the significant global cooling known as the Hirnantian, it is conceivable that other rings may have existed further back in Earth’s history that had a similar climatic effect.
“The idea that rings may have influenced global temperatures further complicates our understanding of how extraterrestrial phenomena may have dictated Earth’s climate,” Tomkins said.
