Could Earth as soon as have had a planetary ring like those round Saturn? Scientists from Monash College in Australia suppose so. In a latest paper they establish 450m-year-old craters that lie near Earth’s historic equator. They suggest these had been attributable to the collapse of a hoop of particles (presumably the remnants of a big asteroid) that after circled the planet. The ring might need lasted tens of thousands and thousands of years, cooling Earth with its shadow. ■
