We recognize Saturn by its magnificent rings, but other planets have smaller and less visible rings, and earth may have had them, too, at one time. Three scientists from Monash University in Australia just published a study explaining how. They studied impact craters from the Ordovician period, around 466 million years ago. Mapping where the earth's tectonic plates would have been at the time, they found that all these craters were within 30 degrees of the equator, while most of earth's dry land was further away. They believe a large asteroid came close to the earth, and was pulverized when it hit the atmosphere. The debris formed rings around the planet that lasted for millions of years, but fell to earth gradually and caused those Ordovician craters.
This theory would also explain the ice age called the Hirnantian Icehouse, which happened near the end of the Ordovician period and was the coldest earth has been in half a billion years. It was a mass extinction event that saw the disappearance of 85% of the earth's marine species. A shadow caused by rings of debris in space would have kept sunlight from reaching the surface. Read a further explanation of these findings in a press release from Monash University. -via Gizmodo
(Image credit: Grebenkov)