Pluto’s Chaotic Mountain Blocks May Have Slid Into Place

In this 3D flyover image compiled from New Horizons data, the high-relief mountain blocks sit surrounded by nitrogen ice downslope of their probable source, the ancient and weathered highlands. Image credit: NASA/JHUAPL/SwRI/Paul Schenk and John Blackwell, Lunar and Planetary Institute

The western edge of Pluto’s Sputnik Planitia is home to a dramatic range of chaotic, fragmentary mountain blocks that rise more than a kilometer above the nitrogen ice plains that fill the basin below. Their high relief, angular appearance, and spectral signature indicate that they are made of the same water ice that forms the crust of the planet, but their lack of consistent structure means that it is unlikely they formed due to the more familiar forms of tectonic mountain-building processes. Research led by Sean O’Hara of the Lunar and Planetary Institute suggests a novel formation mechanism for this chaotic terrain: the blocks may be disrupted pieces of crust that slid down the slope of the Sputnik Planitia basin. O’Hara and collaborator Andrew Dombard of the University of Illinois at Chicago calculated the forces required for a mountain block to slide downslope under its own gravity, accounting for the effects of friction at its base and how the nitrogen surrounding it would both aid and impede its movement. They conclude that the blocks could be quickly emplaced if liquid nitrogen was present at the base of the blocks, which could occur during warm periods of Pluto’s climate. This observation adds to the growing body of evidence that periods of climate change on Pluto had a major hand in sculpting the unique landscape of this far-away world. READ MORE