When a helicopter pilot spotted the first crater in summer 2014, everyone was baffled.
The 100-foot-wide hole appeared on the Yamal Peninsula seemingly out of nowhere, during a tense season of Russian military action in Ukraine and international sanctions.
And then more appeared. Lacking a better explanation, aliens and underground missiles were floated as possible theories, according The Washington Post.
But the truth is that the holes might come from a threat not even Mulder and Scully are equipped to handle: climate change.
Scientific American reports that Arctic zones are warming at a breakneck pace, and summer 2014 was warmer than average by an alarming 9 degrees Fahrenheit, according to anotherstory in Nature. As a result, scientists at the National Oceanic and Atmospheric Administration (NOAA) think that permafrost, the permanently frozen ground that covers the tundra, is starting to thaw in these warmer temperatures.