silicate volcanism, involving basaltic lava with mafic to ultramafic (magnesium-rich) compositions, was confirmed by the "galileo" spacecraft in the 1990s and 2000s from temperature measurements of io's numerous hot spots, locations where thermal emission is detected, and from spectral measurements of io's dark material. temperature measurements from "galileo"<nowiki>'s</nowiki> solid-state imager (ssi) and near-infrared mapping spectrometer (nims) revealed numerous hot spots with high-temperature components ranging from at least to a maximum of , like at the pillan patera eruption in 1997. initial estimates during the course of the "galileo" mission suggesting eruption temperatures approaching have since proven to be overestimates because the wrong thermal models were used to calculate the temperatures. spectral observations of io's dark material suggested the presence of orthopyroxenes, such as enstatite, magnesium-rich silicate minerals common in mafic and ultramafic basalt. this dark material is seen in volcanic pits, fresh lava flows, and pyroclastic deposits surrounding recent, explosive volcanic eruptions. based on the measured temperature of the lava and the spectral measurements, some of the lava may be analogous to terrestrial komatiites. compressional superheating, which could increase the temperature of magma during ascent to the surface during an eruption, may also be a factor in some of the higher temperature eruptions.