A history of high-temperature Io volcanism: February 1995 to May 1997

Ground-based observations of Io's infrared thermal emission between February 1995 and May 1997 show several discrete brightenings for which we can constrain locations, fluxes, and durations. Several of these were brief high-temperature events, with temperatures up to at least 1500 K, similar to but often smaller than the rare “outbursts” seen previously. Loki, Io's most powerful volcano, was relatively active before and probably during Galileo's December 1995 Io flyby, was faint during most of 1996, and began a major, long-lived brightening between February 20 and March 12 1997. Thermal emission was not seen from Ra Patera, site of an active plume in Galileo images. Major outbursts were seen on March 2nd and September 27 1995.