Scientists are closing in on what caused three massive holes to open up mysteriously in northern Siberia last July.
This week a team of Russian researchers roped their way down 34 feet to the bottom of the largest crater and found no evidence of alien beings or meteorites that some people had offered up as possible explanations.
"We managed to go down into the funnel, all was successful," Vladimir Pushkarev, director of the Russian Center of Arctic Exploration and the leader of the team, told The Siberian Times. "We took all the probes we planned, and made measurements. Now scientists need time to process all the data and only then can they draw conclusions."
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So what did cause the holes to form? According to Pushkarev, the leading theory is that the holes were created by pockets of gas that exploded underground.
"As of now we don't see anything dangerous in the sudden appearance of such holes," he told The Siberian Times, "but we've got to study them properly to make absolutely sure we understand the nature of their appearance and don't need to be afraid about them."