Is There Explosive Volcanic Activity on Venus?

Explosive volcanic activity on Venus: The roles of volatile contribution, degassing, and external environment

Authors:

Airey et al

Abstract:

We investigate the conditions that will promote explosive volcanic activity on Venus. Conduit processes were simulated using a steady-state, isothermal, homogeneous flow model in tandem with a degassing model. The response of exit pressure, exit velocity, and degree of volatile exsolution was explored over a range of volatile concentrations (H2O and CO2), magma temperatures, vent altitudes, and conduit geometries relevant to the Venusian environment. We find that the addition of CO2 to an H2O-driven eruption increases the final pressure, velocity, and volume fraction gas. Increasing vent elevation leads to a greater degree of magma fragmentation, due to the decrease in the final pressure at the vent, resulting in a greater likelihood of explosive activity. Increasing the magmatic temperature generates higher final pressures, greater velocities, and lower final volume fraction gas values with a correspondingly lower chance of explosive volcanism. Cross-sectionally smaller, and/or deeper, conduits were more conducive to explosive activity. Model runs show that for an explosive eruption to occur at Scathach Fluctus, at Venus’ mean planetary radius (MPR), 4.5% H2O or 3% H2O with 3% CO2 (from a 25 m radius conduit) would be required to initiate fragmentation; at Ma’at Mons (~9 km above MPR) only ~2% H2O is required. A buoyant plume model was used to investigate plume behaviour. It was found that it was not possible to achieve a buoyant column from a 25 m radius conduit at Scathach Fluctus, but a buoyant column reaching up to ~20 km above the vent could be generated at Ma’at Mons with an H2O concentration of 4.7% (at 1300 K) or a mixed volatile concentration of 3% H2O with 3% CO2 (at 1200 K). We also estimate the flux of volcanic gases to the lower atmosphere of Venus, should explosive volcanism occur. Model results suggest explosive activity at Scathach Fluctus would result in an H2O flux of ~107 kg s−1. Were Scathach Fluctus emplaced in a single event, our model suggests that it may have been emplaced in a period of ~15 days, supplying 1-2×104 Mt H2O to the atmosphere locally. An eruption of this scale might increase local atmospheric H2O abundance by several ppm over an area large enough to be detectable by near-infrared nightside sounding using the 1.18 µm spectral window such as that carried out by the Venus Express/VIRTIS spectrometer. Further interrogation of the VIRTIS dataset is recommended to search for ongoing volcanism on Venus.

High-priority Sites for Lunar Polar Volatiles

High-priority lunar landing sites for in situ and sample return studies of polar volatiles

Authors:

Lemelin et al

Abstract:

Our understanding of the Moon has advanced greatly over the last several decades thanks to analyses of Apollo samples and lunar meteorites, and recent lunar orbital missions. Notably, it is now thought that the lunar poles may be much more enriched in H2O and other volatile chemical species than the equatorial regions sampled during the Apollo missions. The equatorial regions sampled, themselves, contain more H2O than previously thought. A new lunar mission to a polar region is therefore of great interest; it could provide a measure of the sources and processes that deliver volatiles while also evaluating the potential in situ resource utilization value they may have for human exploration. In this study, we determine the optimal sites for studying lunar volatiles by conducting a quantitative GIS-based spatial analysis of multiple relevant datasets. The datasets include the locations of permanently shadowed regions, thermal analyses of the lunar surface, and hydrogen abundances. We provide maps of the lunar surface showing areas of high scientific interest, including five regions near the lunar north pole and seven regions near the lunar south pole that have the highest scientific potential according to rational search criteria. At two of these sites—a region we call the “Intercrater Polar Highlands” (IPH) near the north pole, and Amundsen crater near the south pole—we provide a more detailed assessment of landing sites, sample locations, and exploration strategies best suited for future human or robotic exploration missions.