RECENT VOLCANIC ACTIVITY ON VENUS - EVIDENCE FROM RADIOTHERMAL EMISSIVITY MEASUREMENTS

Most highlands on Venus have summit areas that display low radiothermal emissivity. This is thought to result from weathering of primary rock, which at high altitudes (relatively low temperatures) produces a distinctive pyrite-bearing high-dielectric-constant mineral asemblage. This paper treats exceptions to the rule, high-emissivity peaks at high altitudes and low-emissivity domes at low altitudes, which are related to volcanism on Venus. Low-emissivity plains domes tend to be spatially correlated with volcanoes having high-emissivity summits. Both phenomena are interpreted to be manifestations of relatively recent volcanism: the volcano summits display high emissivity because flows on them are too young to have had time to weather to the low-emissivity mineral assemblage, and nearby small volcanic domes on the plains are still seeping volcanic gases which, permeating the pore space of the plains soil layer, make the high-dielectric-constant pyritic mineral assemblage stable at the higher temperatures of plains altitudes. Of the volcanoes studied, Maat Mons has undergone the most recent major episode of volcanic activity. © 1993 by Academic Press, Inc.