Rosetta, the spacecraft launched by the European Space Agency in August 2014 to orbit and probe Comet 67P, has captured new images of the comet using its OSIRIS instrument. It showed that there are large and deep depressions in the comet's surface. Scientists who analyzed these pockmarks say they appear to be giant sinkholes, with some of them still actively shifting.

The depressions were found clustered in one region, in the rubber-duck-shaped comet's northern hemisphere, according to LA Times. Scientists are now trying to learn more about why these sinkholes appeared. They believe that the surface below the icy comet is vaporizing as it moves closer to the sun, so it can no longer support the crust. 

"They are almost as deep as they are wide," said Jean-Baptiste Vincent of the Max Planck Institute for Solar System Research in Göttingen, Germany, via the BBC. "The largest one is about 200m wide and 200m deep. It's amazing because it gives us the possibility to look inside the comet for the first time," he remarked.

The scientists further studied the depressions using computer models. "We thought these pits had to be the source of the explosion, but when we did simulations, we found that just 100,000 kg of material had been ejected, "said Dennis Bodewits of the University of Maryland, according to the LA Times. "That sounds like a lot, but that would make a small hole of just a few meters, not a pit." 

"That tells you something about the scale of these things. They are really strange." Bodewits added.

Rosetta's discovery is giving scientists a clearer view of the comet's interiors, providing a better study of its fundamental structure. "We can really see the texture several hundred meters underneath the surface," the scientist further said. "By themselves, they are giving us part of the story."

Comet 67P and Rosetta are now located 290 million km from the Earth. During its probe last November, Rosetta dropped the lander, Philae, on the comet's surface and the scientists are hoping it will be able to radio data on the cavities soon.

Their findings was published in the journal Nature.