Theoretical modeling of eruption plumes on Mars under current and past climates

We have used a combined conduit transport/eruption column model to explore the evolution of volcanic eruption plumes on Mars under different atmospheric conditions. In the calculations we consider a volatile phase composed of H 2 O, CO 2 , and SO 2 and take into account that the magmatic water erupted at the vent may condense as the eruption column rises into the Martian atmosphere. As two end‐member models, we explore the eruption of rhyolitic and basaltic melt compositions containing different amounts of volatiles as well as having different eruption temperatures. Under current Martian atmospheric conditions eruption plumes are found to rise as high as 100 km for a mass eruption rate of 5×10 7 kg s −1 , which is consistent with model calculations by Wilson and Head [1994]. In contrast, under a dense atmosphere (10 5 Pa on the Martian surface) which may have existed earlier in Martian history, the same eruption plume reaches only about 25 km height. All magmatic water released during the eruption is found to freeze as it rises in the eruption column, which means that fallout from the plume will contain water ice which can be subsequently deposited in near surface layers. This ice may then suddenly melt due to higher surface heat flow or shallow intrusions leading to rapid release of water on the flanks of volcanoes. Only if the atmosphere were hotter in the past could the water in the eruption plume condense and produce rain rather than ice. Furthermore, the calculations show that smaller micron‐size particles would be distributed globally from eruption plumes under current Martian conditions but would not have been as widely dispersed from plumes erupted into an earlier dense atmosphere.