Sublimation-driven convection in Sputnik Planitia on Pluto.

Sputnik Planitia is a nitrogen-ice-filled basin on Pluto. Its polygonal surface patterns have been previously explained as a result of solid-state convection with either an imposed heat flow or a temperature difference within the 10-km-thick ice layer. Neither explanation is satisfactory, because they do not exhibit surface topography with the observed pattern: flat polygons delimited by narrow troughs.