Prominent volcanic source of volatiles in the south polar region of the Moon

Abstract Gas-rich discharges of magma produced pyroclastic vents on the lunar surface. Calculations suggest those pyroclastic vents repeatedly generated 1012 to 1015 g of H2O and CO + CO2 for pyroclastic volumes of 10 to 500 km3 early in lunar history, particularly during the first billion years of lunar history. Some of those volatiles migrated to the lunar poles where they could be trapped in permanently shadowed regions (PSRs). The largest indigenous source of volatiles in the south polar region was volcanism that occurred on the floor of the Schrodinger impact basin. Here a large pyroclastic vent ceased erupting ∼ 3.70 +0.02-0.03 Ga, releasing H2O, CO-CO2, F, S, and Cl vapor species, including calculated values of 3.0 × 1013 to 1.6 × 1014 g H2O. A transport and depositional model suggests 1.1 × 1010 kg (12%) of that water may have been trapped in the south polar region.