  The far-infrared (far-IR) spectral window plays host to a wide range of
spectroscopic diagnostics with which to study planetary disk systems and
exoplanets at wavelengths completely blocked by the Earth atmosphere. These
include the thermal emission of dusty belts in debris disks, the water ice
features in the "snow lines" of protoplanetary disks, as well as many key
chemical species (O, OH, H2O, NH3, HD, etc). These tracers play a critical
diagnostic role in a number of key areas including the early stages of planet
formation and potentially, exoplanets. The proposed Japanese-led IR space
telescope SPICA, with its 3m-class cooled mirror (~5 K) will be the next step
in sensitivity after ESA's Herschel Space Observatory (successfully launched in
May 2009). SPICA is a candidate "M-mission" in ESA's Cosmic Vision~2015-2025
process. We summarize the science possibilities of SAFARI: a far-IR
imaging-spectrometer (covering the ~34-210um band) that is one of a suite of
instruments for SPICA.
