An enormous hole has appeared in northern Siberia, sparking a number of theories about what caused the crater.
The hole was found in the gas-rich region of Yamal - which means "end of the world" in the local Nenets language - and is believed to be up to 80 metres wide.
The opening is about 30 kilometres from the area's largest gas field and is thought to have first appeared about two years ago but went unseen until recently spotted by a helicopter.
A Russian government official rejected one theory - that the hole was the result of a meteorite striking the Earth.
A team of scientists is due to arrive at the scene on Wednesday to take samples of soil, air and water to determine what caused the hole.
The Siberian Times reported that Anna Kurchatova, from the Sub-Arctic Scientific Research Centre, believed that the crater was formed by a mixture of water, salt and gas that ignited to create an underground explosion.
However, Dr Chris Fogwill, a polar scientist at the University of New South Wales, told the Sydney Morning Herald that it was more likely to be a geological phenomenon known as a pingo.
A pingo is a block of ice that has developed into a small hill in the frozen ground. The ice can eventually push through the earth to leave a crater when it melts.
The Yamal Peninsula is Russia's main gas-producing area and is mostly pemafrost because of its proximity to the Arctic.