My primary research focus is on theoretical investigations of physical and chemical processes in planetary atmospheres, with a particular emphasis on photochemical modeling of planetary and satellite atmospheres, aerosol formation and microphysics, upper atmospheres/aeronomy, and atmosphere-surface interactions. I am currently investigating the possibility and consequences of photochemistry and haze production in extrasolar giant planets, brown dwarfs, and giant planets within our own solar system. I am also examining the possible sources, total influx rate, and photochemical implications of the influx of external material into giant-planet atmospheres; comparing photochemical models of the giant planets with observational data in an attempt to understand physical and chemical processes taking place in the stratospheres and tropospheres of these planets; and modeling the photochemistry of possible volcanic atmospheres on Io.