7. Plutos Mysterious Floating Hills
It turns out that Pluto's famous heart is one of the most interesting things about it. Informally named Sputnik Planum, the area is essentially an enormous icy plane around 1,000 miles across and is surrounded by a dramatic border of mountains. The ice, however, is not as we know it here on Earth. Due to Pluto's frankly chilly surface temperatures (somewhere in the region of -230°C), many of the elements that exist on Earth as a liquid or even a gas, are frozen into solids of different densities. On these great planes, mountains of water ice "float" on a sea of frozen nitrogen. Because water ice is less dense than nitrogen ice, scientists think that these enormous icebergs cruise around the heart after breaking away from the highlands around the edge. This means that Pluto's heart is not a static frozen wasteland but a
constantly shifting and changing frozen wasteland, with the ice flowing around in a similar fashion to glaciers here on Earth. To get a really good look, check out
this super high-resolution image of the ice planes of Pluto.
