A baffling 80-meter-wide hole has appeared out of nowhere in Siberia, The Sydney Morning Herald reports. Is it a meteor crater, or signs of an underground explosion? Probably not, says one polar scientist who thinks it’s simply a collapsed pingo. Pingos are blocks of ice below ground that form mounds; when they melt, they can leave behind large craters. Because Earth’s temperatures are warming, researchers expect to see more and more of these holes in Arctic regions.