Pappalardo's research focuses on processes that have shaped the icy satellites of the outer solar system, especially Europa and the role of its probable subsurface ocean. Europa research includes the possibility that solid-state convection has played an important role in the satellite's history, investigation of regions of separation and spreading of the satellite's icy lithosphere, and implications of surface geology for lithospheric properties and the existence of a liquid water ocean beneath the icy surface. Additional recent research involves the nature, origin, and evolution of bright grooved terrain on Jupiter's moon Ganymede, and the geological history of Saturn's moons Enceladus and Titan. Recent research relates to the relative roles of tectonics, icy volcanism, and mass wasting in shaping icy satellite surfaces.