Quantifying the Eruptive Flux on Venus With VenSAR Informed by Observations From Earth and Io

The current volcanic output of Venus is unknown. In the 2030s, the VenSAR (Venus Synthetic Aperture Radar) instrument onboard the European Space Agency's (ESA) EnVision mission will estimate the global volcanic mass flux by looking for new flows with radar imaging at resolutions of 10 or 30 m/pixel, which can be compared with the 1990s?era Magellan data (100–300 m/pixel). Based on eruptions on Earth and Io, we make suggestions for measuring the Venusian global eruptive flux. We do not need to observe small eruptions with Eruption Magnitude (based on mass) <3 because (at least on Earth) they produce <10% of the aggregate erupted mass. Assuming that the size–frequency distribution of Earth lava flows and domes holds on Venus and is augmented to include flows 75% longer as predicted for the Venus surface, we find that all Eruption Magnitude ?3 eruptions are detectable by VenSAR–VenSAR imaging and >80% by VenSAR–Magellan. However, only 80% of eruptions may produce a detectable change in radar backscatter based on our examination of 24 basaltic terrestrial lava flows from 2014 to 2023 from the ESA Sentinel?1a/b satellites. From observed Earth basaltic flows, thickness will rarely be measured on Venus due to low vertical accuracy. If VenSAR images 20%–40% of the most active volcanoes (as planned), it could detect 79%–92% of the flux if the Eruption Magnitude–frequency distribution is similar to Earth and Io. A few eruptions could then be extrapolated to a global flux, but this is dependent on quantifying the largest eruption, so targeting the right volcanoes is critical.