() – Famous for its extensive ring system, Saturn is one of four planets in our solar system that possess this distinctive feature. And now, scientists hypothesize that Earth may have sported its own ring about 466 million years ago.
Planet Earth experienced a spike in meteorite impacts during the Ordovician perioda time of significant change for Earth’s life forms, plate tectonics, and climate. According to a study published on September 12 in the academic journal Earth and Planetary Science Lettersnearly two dozen known impact craters during this era were all within 30 degrees of Earth’s equator, indicating that meteoroids could have rained down from a rocky ring around the planet.
“It is statistically unusual that there are 21 craters all relatively close to the equator. It shouldn’t happen. “They should be randomly distributed,” said lead author Andrew Tomkins, a geologist and professor of Earth and Planetary Sciences at Monash University in Melbourne, Australia.
The new hypothesis not only sheds light on the origins of the spike in meteorite impacts, but may also provide an answer to a hitherto unexplained event: a global deep freeze, one of the coldest climate events in Earth’s history, may to have been the result of the shadow of the ring.
Scientists hope to learn more about the possible ring. It could help answer mysteries of Earth’s history, as well as raise new questions about the influence an ancient ring might have had on evolutionary development, according to Tomkins.
When a smaller object gets close enough to a planet, it reaches what is known as Roche limitthe distance at which the celestial body has enough gravitational force to break the approaching body. The resulting debris then creates rings around the planet, like those around Saturn, which may have formed from the remains of icy moons, according to NASA.
Scientists previously believed that a large asteroid broke apart within the solar system, creating the meteorites that hit Earth during the Ordovician period. However, such an impact would likely have caused the impacts to be distributed more randomly, like craters on the Moon, Tomkins explained.
The study’s authors hypothesize that a large asteroid, estimated to be about 12 kilometers (7.5 miles) in diameter, instead reached Earth’s Roche limit, which could have been about 15,800 kilometers (9,800 miles) of the planet, based on measurements of asteroid debris from the past. The asteroid would have been largely battered by other collisions, which would have made the debris loose and easy to separate by Earth’s tidal force, according to Tomkins.
The ring would have formed along the equator due to the Earth’s equatorial bulge, similar to how the rings of Saturn, Jupiter, Uranus and Neptune are also found around the equatorial planes of each of those planets, he added. .
About 200 impacts are known throughout Earth’s history, Tomkins said. By looking at how Earth’s continental masses moved over time, the authors discovered that the 21 known craters dating to the Ordovician period were all near the equator. Furthermore, only 30% of the Earth’s land surface suitable for preserving a crater was near the equator. If the impacts were random and not from a ring, most of the craters should have formed far from the equator, he added.
The authors also point out a study February 2022 that analyzed impact craters on Earth, the Moon, and Mars, and found evidence of the Ordovician impact peak only on Earth, adding more evidence that aligns with the ring theory.
“The study presents a nice idea that brings together some mysteries,” said astrophysicist Vincent Eke, an associate professor at the Institute of Computational Cosmology at Britain’s Durham University, who was not involved in the new study.
The research analysis found several deposits around Earth from the same era as the impact craters that contained high levels of L-chondrite, a common meteoritic material, which showed signs of shorter exposure to space radiation than the meteorites that are found today. The finding suggests that a large space meteorite asteroid that likely drifted within Earth’s Roche limit broke up near the planet, the study authors wrote.
A few million years after the period of increased meteorite impacts, about 445 million years ago, there was a dramatic drop in Earth’s global temperatures known as the He was Hirnatian.
“Later remnants of such an event (a possible ring) could explain these three observations,” Eke said in an email, referring to impact craters, meteorite debris and global climate change.
The study’s authors are investigating what degree of shading would be necessary to trigger a deep global freeze, a finding that could in turn help estimate how opaque the ring was, Tomkins said. Likewise, the Earth could have been cooled by dust clouds from meteorite impacts, he added.
Tomkins said he hopes future research will establish how long the ring persisted and shed light on how it may have influenced the evolutionary changes Earth faced, likely due to difficult climatic conditions.
“Understanding the causes of Earth’s climate change can help us also think about (the) evolution of life,” he added.
It’s hard to say what such a ring would have looked like without knowing the density of the material, but Tomkins estimates that even a faint ring would have been visible from Earth.
“If you were on the night side of the Earth looking up, and the sunlight was shining on the rings, but not on you, that would probably make it quite interestingly visible, it would be quite spectacular,” he said.
Based on the length of the global cooling period and the dating of craters and meteorite material, the possible Earth ring could have lasted between 20 and 40 million years, according to Tomkins. Collisions between other particles would have caused space rocks to be launched out of the ring.
Previous research discovered that ancient Mars could also have sported a ring, or rings, and scientists predict that planet could have more in the future.
“Although rings are currently associated with the solar system’s outer giant planets, in the next 100 million years or so, Mars should acquire a ring system as its inner moon, Phobos, spirals into the rigid Roche radius. and it is torn in turn,” Eke said in an email. “Fortunately, for the development of life on Earth, these types of (events) are rare today.”
Since the end of September, an asteroid called 2024 PT5 has been traveling close to Earth. The space rock is commonly known as a “minimoon” because it comes within 4.5 million kilometers (2.8 million miles) of the planet. However, even during the asteroid’s closest pass to date, on August 8, at about 352,300 miles (567,000 kilometers), it was nowhere near Earth’s Roche limit, said Carlos de la Fuente Marcos, researcher at the Faculty of Mathematical Sciences of the Complutense University of Madrid who has studied the minimoon. De la Fuente Marcos was not involved in the new study.
Furthermore, the suggested Earth ring “would have been the result of the disruption of a much larger body, as the authors indicate in their paper,” he added in an email, so the asteroid, probably about 37 feet (11 meters) in diameter, could not have created a new ring for the Earth.
“You would have to capture a big one and put it in exactly the right orbit for it to break up… (This minimoon) is just one example of the processes that take place in our nearby space area and that can give rise to the type of things we are about speaking,” Tomkins said. However, “this ring formation event we believe may have occurred only once in the last 500 million years.”
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