analysis of "voyager" images led scientists to believe that the lava flows on io were composed mostly of various forms of molten elemental sulfur. the colouration of the flows was found to be similar to its various allotropes. differences in the lava colour and brightness are a function of the temperature of polyatomic sulfur and the packing and bonding of its atoms. an analysis of the flows that radiate out from ra patera revealed differently colored materials, all associated with liquid sulfur, at different distances from the vent: dark albedo material close to the vent at , red material in the central part of each flow at , and orange material at the farthest ends of each flow at . this colour pattern corresponds to flows radiating out from a central vent, cooling as the lava travels away from it. in addition, temperature measurements of thermal emission at loki patera taken by "voyager 1"<nowiki>'s</nowiki> infrared interferometer spectrometer and radiometer (iris) instrument were consistent with sulfur volcanism. however, the iris instrument was not capable of detecting wavelengths that are indicative of higher temperatures. this meant that temperatures consistent with silicate volcanism were not discovered by "voyager". despite this, "voyager" scientists deduced that silicates must play a role in io's youthful appearance, from its high density and the need for silicates to support the steep slopes along patera walls. the contradiction between the structural evidence and the spectral and temperature data following the "voyager" flybys led to a debate in the planetary science community regarding the composition of io's lava flows, whether they were composed of silicate or sulfurous materials.