Pluto’s “Washboard Terrain”: Evidence of Ancient Glaciers

Pluto’s terrain shows a “washboard” pattern of fine ridges just north of its great frozen nitrogen sea, Sputnik Planitia. A recent study by the New Horizons team argues that the ridges are deposits of water ice left behind as an ancient frozen nitrogen glacier that once covered the area sublimed away. Water-ice is buoyant in nitrogen ice and is expected to collect in pits formed on the surface of the glacier as the nitrogen sublimes. NOAO Astronomer Tod Lauer is a coauthor on the study.