Researchers mapped the Ordovician-era craters using plate tectonic reconstructions and identified a peculiar pattern: all 21 known impact sites from this period are located within 30 degrees of the equator. This distribution is surprising, as more than 70% of Earth's continental crust lies outside these equatorial latitudes. Typically, asteroid impacts on a planetary surface, such as those observed on the Moon or Mars, are randomly distributed. Yet here, the Ordovician impact craters are highly concentrated, leading scientists to believe something unique was at play.

The researchers hypothesize that a large asteroid entered Earth's vicinity, crossing into a region known as the Roche limit, where tidal forces would have torn it apart. "When an object crosses this boundary, it disintegrates due to gravitational forces," explained lead author Professor Andy Tomkins from Monash University in Australia. He added that the resulting debris could have formed a ring system, similar to those seen around gas giants like Saturn. Over millions of years, the ring's particles would have gradually fallen to Earth, accounting for the spike in meteorite impacts observed in geological layers from that period. "We see extraordinary amounts of meteorite debris in sedimentary rocks from the Ordovician, further suggesting a prolonged fallout from a ring system," said Tomkins.

Intriguingly, this possible ring system may have influenced Earth's climate. If a debris ring surrounded the planet, it might have cast a shadow over parts of Earth, reducing sunlight and potentially triggering a cooling period. The research team suggests that this shadow could have contributed to a significant climate event known as the Hirnantian Icehouse, one of the coldest intervals in Earth's last 500 million years. "The idea that a ring system could have had such profound climate effects opens up a new layer of complexity in understanding Earth's climate history," remarked Tomkins. This new model introduces the concept that extraterrestrial events may have played a larger role in shaping Earth's climate than previously considered.