Nitrogen ice glaciers on Pluto appear to carry numerous hills that may be fragments of water ice, according to NASA, which has analyzed images and data from the New Horizons spacecraft.

The hills, which measure several miles across, are in the vast plain on the dwarf planet’s surface dubbed ‘Sputnik Planum’ by scientists. “They are yet another example of Pluto’s fascinating and abundant geological activity,” explained NASA, in a statement on its website.

Related: New Pluto photos show breathtaking views of dwarf planet

NASA notes that, because water ice is less dense than nitrogen-dominated ice, scientists believe the hills are floating in “a sea of frozen nitrogen” and move like icebergs in Earth’s Arctic Ocean.

“The hills are likely fragments of the rugged uplands that have broken away and are being carried by the nitrogen glaciers into Sputnik Planum,” said NASA. “‘Chains’ of the drifting hills are formed along the flow paths of the glaciers.”

Related: Stunning NASA image shows Pluto's atmosphere

NASA recently released stunning pictures that show Pluto’s landscape in incredible detail. The space agency also posted an image of the haze layers in Pluto’s atmosphere taken by the New Horizons spacecraft