Researchers gathering information via the Rosetta Probe as it explores Comet 67P have learned a lot about the celestial body, but even they were stunned by a recent discovery.

This Dec. 21, 2014 photo made by the European Space Agency's Rosetta spacecraft and provided by researchers led by Jean-Baptiste Vincent shows the most active pit, known as Seth_01, which scientists believe is one of several sinkholes on the comet 67P/Churyumov-Gerasimenko.

(Vincent et al., Nature Publishing Group, ESA via AP)

New analysis shows that the speeding mass of rock and ice hassinkholes. The depressions were noticed early on when Rosetta was still traveling at a relatively great distance away.

At the time, they didn’t know quite what to make of them, but as the probe moved closer, there was better opportunity to take high-resolution images. It was then learned that there are 18 sinkholes dotting the northern hemisphere of the comet.

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Their formation process was likely similar to the one that occurs here on Earth. Subterranean materials erode until there’s no longer a strong enough support system for the ground above, and it collapses.

The large difference is that on 67P, the breaking down of natural materials doesn’t involve water, as liquids can’t form in the environment. What happens there is that ice turns directly into gas and just floats away.

Now that scientists can see more of the comet’s interior, they’re looking forward to learning more about its structure.

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The Rosetta Spacecraft took an intimate Valentine's Day photo series of Comet 67P. (ESA/Rosetta/NavCam)