In the middle of last summer came news of a bizarre occurrence no one could explain. Seemingly out of nowhere, a massive crater appeared in one of the planet's most inhospitable lands. Early estimates said the crater, nestled in a land called "the ends of the Earth" where temperatures can sink far below zero, yawned nearly 30 metres in diameter.

The saga deepened. The Siberian crater wasn't alone. There were two more, ratcheting up the tension in a drama that hit its climax as a probable explanation surfaced. Climate change had thawed the permafrost, which had caused methane trapped inside the icy ground to explode. "Gas pressure increased until it was high enough to push away the overlaying layers in a powerful injection, forming the crater," one German scientist said at the time.

Now, however, researchers fear there are more craters than anyone knew — and the repercussions could be huge. Russian scientists have now spotted a total of seven craters, five of which are in the Yamal Peninsula. Two of those holes have since turned into lakes. And one giant crater is rimmed by a ring of at least 20 mini-craters, the Siberian Times reported. Dozens more Siberian craters are likely still out there, said Moscow scientist Vasily Bogoyavlensky of the Oil and Gas Research Institute, calling for an "urgent" investigation.

He fears that if temperatures continue to rise — and they were five degrees higher than average in 2012 and 2013 — more craters will emerge in an area awash in gas fields vital to the national economy. "It is important not to scare people, but to understand that it is a very serious problem and we must research this," he told the Siberian Times. "We must research this phenomenon urgently, to prevent possible disasters."