The mystery of the Siberian craters is one step closer to being solved. Earlier this week, Russian scientists descended into one of the massive craters that was discovered in Siberia over the summer. Vladimir Pushkarev, director of the Russian Centre of Arctic Exploration, and his team climbed down around 16.5 meters (54 feet) to the base of the crater, according to The Siberian Times.

At the bottom, they examined a frozen lake that extends down another 10.5 meters (34.4 feet) below the icy surface, and collected samples for further analysis. It's not clear what exactly caused the three craters to form. Some scientists have theorized that methane gas released due to climate change might have caused the frozen Siberian permafrost to collapse.

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