We reported recently on the major discovery by NASA via its New Horizons spacecraft of a massive crack splitting the surface of Pluto’s moon Charon — and that crack tells the story of a world that is so dark and cold, it’s difficult for us to even imagine.

Scientists believe that Charon once had a large subsurface ocean of water, but eventually it froze over and, like the Hulk, burst through the crust of the moon, creating tremendous cracks in the surface. Charon is currently covered in water ice, but scientists think that at one point it could have been warm enough to be in liquid form, pooling beneath its barren surface.

Those days are long gone. Now, Charon is one of the coldest places imaginable — even physically possible.

Pluto and Charon are both very cold places, situated way too far from our sun to get the kind of warmth we enjoy here on Earth. And for Charon, that takes temperatures to their physical extremes. During the winter, temperature on the surface of Charon dips to a frigid -258 degrees Celsius. The absolute coldest temperature it is possible to reach based on our understanding of physics is -273.15 degrees Celsius, which would amount to -459.67 degrees Fahrenheit and absolute zero kelvin. At that temperature, atoms completely stop moving.

It is because of Charon’s extremely cold temperatures that scientists believe it has a giant red spot at its north pole. Scientists think those are gases sucked over from Pluto that get super-cooled so fast that they skip the liquid stage and go right to a solid stage called tholins.

It’s yet more fascinating details we continue to learn thanks to the New Horizons spacecraft, and with much more data yet to be sent back, we may continue to make new discoveries about Charon and Pluto.