High contrast imaging with GPI has the potential to:
a) Characterize the surface and atmospheric composition of Galilean satellites and Titan, and monitor the volcanic activity of Io, pinning down the highest temperature of the magma (McEwen et al. 1998; Marchis et al. 2002);
b) Determine size, shape, surface morphology and composition of the 50 largest main-belt asteroids, search for multiplicity, and hence yield information about the bulk density and the formation of this remnant of the solar system formation (Merline, et al. 2002; Marchis et al. 2003);
c) Monitor the atmospheric activity of Uranus and Neptune, focusing especially on the cloud formation and wind profile above the stratospheric haze near the southern pole of Uranus, which is now being exposed to sunlight (Rages et al. 2004). Study of Neptune’s atmosphere yield information about the transport of energy and the source of its mysterious internal source of heat (Pearl & Conrath 1991).