Pluto's surface exhibits a wide variety of landscapes, results from five new studies in this special issue on the New Horizons mission report. The dwarf planet has more differences than similarities with its large moon, Charon. What's more, the studies in this package reveal, Pluto modifies its space environment - interacting with the solar wind plasma and energetic particles around it. The results pave the way for many further, in-depth studies of Pluto.
NASA's New Horizons mission continues to download information gathered from Pluto and its moon Charon during its historic flyby on 14 July, 2015. As this data arrives on Earth, scientists process and study it. In the first of five papers in this package, Jeffrey Moore et al. offer some of the first descriptions of the wide array of geological features on Pluto and Charon. They report evidence of tectonics, glacial flow, transport of large water-ice blocks, and broad mounds on Pluto - possibly a result of cryovolcanoes. Data on the variability of terrain suggests the dwarf planet has been frequently resurfaced by processes like erosion, pointing to active geomorphic processes within the last few hundred million years. Such processes have not been active so recently on Charon; divided into a rugged north and a smooth south, the moon is marked with older craters and troughs, contrasting with Pluto.
In a second study, Will Grundy et al. analyze the colors and chemical compositions of the icy surfaces of Pluto and Charon. The volatile ices, including water ice and solid nitrogen, that dominate Pluto's surface are distributed in a complicated way, they report, a result of geomorphic processes acting on the surface over different seasonal and geological timescales. Broad expanses of reddish-brown molecules called tholins accumulated in some parts of Pluto, the study suggests. In a third study, G. Gladstone et al. investigate the atmosphere of Pluto, which is colder and more compact than expected and hosts numerous extensive layers of haze. In a fourth study, Harold Weaver et al. examine the small moons Styx, Nix, Kerberos, and Hydra, which are irregularly shaped, fast rotating and have bright surfaces. Finally, Fran Bagenal et al. report how Pluto modifies its space environment, including interactions with the solar wind and a lack of dust in the system. Taken together, these results from the flyby of Pluto pave the way for scientists' better understanding of processes of planetary evolution.