Several months after a mysterious hole in the ground was discovered on the Yamal Peninsula of northwest Siberia, scientists have worked up the courage to climb down into the crater. While rappelling into the hole this week, the researchers captured a series of stunning images.

Like rock climbers and spelunkers, the scientists used rope and carabiners to repel 54 feet to the bottom of the crater. The Russian Centre of Arctic Exploration team collected samples from the frozen lake that stretches another 34.4 feet below the pit's floor.

"We managed to go down into the funnel, all was successful," Vladimir Pushkarev, director of the center, told The Siberian Times. "We used climbing equipment, and it is easier to do this in winter than in summer, with the ground now hard."

The newly explored crater is one of three holes found earlier this year -- two on the Yamal Peninsula and one on the Taymyr peninsula, to the northeast, which was happened upon by a group of reindeer herders.

Researchers still don't know exactly why or how the holes formed, but some have suggested methane released by warming permafrost could have caused an explosive collapse. Data collected during this week's expedition could help solve the puzzle.

"We took all the probes we planned, and made measurements," Pushkarev said. "Now scientists need time to process all the data and only then can they draw conclusions."