An ocean beneath Sputnik Planitia?

The present location of Sputnik Planitia—the prominent deep icy basin on Pluto—is close to one of the longitudes of the dwarf planet’s tidal axis. By analogy with other large basins in the Solar System, it is thought to be an impact feature. Although reorientation arising from tidal and rotational torques can explain the present-day location of the basin, it requires the feature to be a positive gravity anomaly, despite its negative topography. Francis Nimmo et al. argue that if Sputnik Planitia formed via impact and if Pluto possesses a subsurface ocean, a positive gravity anomaly would naturally result because of shell thinning and ocean uplift, followed by later modest nitrogen deposition. This is one of four papers on the geology of Sputnik Planitia in this issue of Nature. In News & Views, Amy Barr puts these latest contributions into context.