LARGE-SCALE VOLCANIC ACTIVITY AT MAAT-MONS - CAN THIS EXPLAIN FLUCTUATIONS IN ATMOSPHERIC CHEMISTRY OBSERVED BY PIONEER-VENUS

Magellan (and Pioneer Venus Orbiter (PVO)) found high mountain terrain s on Venus (similar to 2.5 km above 6051 km planetary radius) exhibit anomalously low radiothermal emissivity. This is thought to result fro m weathering of primary Venus rock, which at high altitudes produces a distinctive high-dielectric-constant mineral assemblage. Deviations f rom the nominal altitude-emissivity pattern have been used as a crude chronometric tool with which to date Venusian landforms. This techniqu e indicates Maat Mons (an unusually large shield volcano, standing 9.1 7 km above 6051 km planetary radius, at 2.1 degrees N, 194.3 degrees E ) has undergone a ''recent'' episode of large-scale volcanic activity, a deduction also implied morphologically. The present paper investiga tes whether a plinian eruption at Maat Mons could explain the enhanced concentrations of SO2 gas in the upper atmosphere of Venus that were detected by the Pioneer Venus UV spectrometer. The results show for a minimum vent radius of 156 m, a minimum eruption temperature of 1200 K , and a magmatic volatile content of similar to 5 wt%, a plinian erupt ion at the summit of Maat Mons can explain the anomalous concentration of SO2 gas. This would mean Maat Mons is an active volcano.