Present and past glaciation on Pluto

Modern N₂ ice glaciers flow from highlands to the east of the 750 × 1400 km² lowland of Sputnik Planum [SP] and merge with the ices of similar composition on SP. We explore the possibility that glaciation may be fed by N₂ sublimation from SP followed by redeposition on the highlands. The uplands to the northeast, north, and west of SP have been erosionally sculpted into a variety of dissected terrains that feature linear depressions (valleys), locally in dendritic networks. We interpret these dissected terrains to have been carved by N₂ glaciers formerly covering the uplands. Depositional glacial landforms (moraines, eskers, outwash) have not been identified, however. N₂ glaciation would have a different erosional manifestation because the substrate (porous water ice and CH₄-rich mantles) probably has lower density than N₂, and also because of the lack of freeze-thaw weathering. If sufficiently thick (1–4 km), N₂ glaciers might have experienced basal melting. Past flow of N₂ glaciers from the highlands into SP may have detached and transported the prominent mountainous water ice mountains along the western border of SP.