When Earth Had Rings
P lanetary rings may be one of space’s many spectacles, but in our solar system, they’re a dime a dozen. While Saturn’s rings are the brightest and most extensive, Jupiter and Uranus and Neptune have them, too, likely the dwindling remains of shredded asteroids or comets. What’s more, four icy minor planets—Chariklo, Chiron, Quaoar, and Haumea—that orbit among or beyond our gas giants, also host ring systems. Even so, it would be fanciful to imagine that Earth once had a ring system of its own, wouldn’t it? I mean, that just seems almost too cool to be true.
Rings are likely the dwindling remains of shredded asteroids or comets, and when you think about the turbulence Earth experienced around half a billion years ago, the reality of a bygone ring system around Earth seems less farfetched. That’s the case researchers make in a new study published in Earth and Planetary Science Letters.
About 466 million years ago (long before the dinosaurs), the rate of stuff falling on Earth that was large enough to leave craters spiked sharply. Researchers have identified 21 impact craters from this spike, with sizes between a few and 50 kilometers in diameter. And sedimentary rocks from this period show a huge increase—a factor of 100 to 1,000—in the concentration of elements associated with a specific group of meteorites, called L chondrites. This period, the mid-Ordovician, also included an extreme drop in global temperature, roughly 10 degrees Celsius, which coincided with increased seismic and tsunami activity. Also, a mass extinction eliminated 85 percent of marine species, after which the temperature rebounded. What could possibly explain this?
