A giant hole in the Earth found in an area of Siberia so remote the region's name Yamal means "end of the world" has scientists scratching their heads in an effort to explain where it could have come from.
A research team on its way to one of Russia's northernmost points would take water, soil and air samples around the mysterious 250-foot-wide hole, the depth of which has not yet been determined, officials said.
The gigantic pit was first spotted from helicopters operating in the gas-rich Yamal Peninsula, almost within the Arctic Circle.
While it looks like a sinkhole, there's a ring of soil surrounding the circular cavern that apparently was thrown outside of the opening, experts said.
Various theories about the origin of the cavity, ranging from an underground explosion to a meteor impact, have been put forward.
Melting of the Siberian caused by global warming could have released methane or other gases trapped in the ice, Anna Kurchatova from the Sub-Arctic Scientific Research Center told the Siberian Times.
The gases may have mixed with water and salt underground resulting in an underground explosion, she said, adding that the resulting explosion would have been like the cork popping off the top of a champagne bottle.
That possibility is strengthened by the hole's proximity to the biggest natural gas field in the area, experts said, which was discovered in 1972 and has been producing significant percentages of Siberia's gas production.
Much of that gas is exported to the rest of the world.
The possibility of a meteor impact has been discounted, a spokesman with the Yamal branch of the Emergiencies Ministry said, but further examination would be needed to determine it origin.
"We can definitely say that it is not a meteorite," the spokesman said. "No details yet."
The giant crater and hole was probably created about 2 years ago, scientists said.
The Yamal region is well known for its huge herds of reindeer, and is of great interest to paleontologists who have recovered the preserved remains of woolly mammoths who once roamed the area.