Investigation of imagery and other data from the approaching probe reveal Pluto to be larger than previous estimates. Principal investigator Alan Stern explains the implications on ice composition, rock estimates, and atmospheric composition. ---- Full StorY: goo.gl/ZptciN Pluto at Last! NASA Spacecraft Arrives for Dwarf Planet Close-Up Tuesday: goo.gl/YVocJz NASA/JHUAPL/SwRI/Pluto color image enhanced by Kevin M. Gill/Edited by Space.com's @SteveSpaleta