Beneath the dwarf planet’s surface, ice flows like lava
The unique hills of Pluto’s icy heart-shaped region were probably formed by cryovolcanism – when water and ice act like lava and rock.
“Rather than erosion, cryovolcanic activity appears to have extruded large amounts of material onto Pluto’s exterior and resurfaced an entire region of the hemisphere New Horizons saw up close,” says Kelsi Singer from New Horizons, which flew past Pluto in 2015.
The region in question is the bright plain called Sputnik Planitia. Close inspection of New Horizons images of the region show it is covered in huge domes up to 7km tall and 100km wide, which the study found could be created by repeated cryovolcanic eruptions of material with a toothpaste-like consistency.
Few if any craters exist in the area, indicating it is geologically young. This raises the possibility that Pluto’s interior structure retained heat into the relatively recent past, to make it possible for material to be deposited on the surface. http://pluto.jhuapl.edu/