Progress Towards Balloon-Based Seismic Studies on Venus

Seismology is essential for understanding a planets interior structure and evolution. However, on Venus, high surface temperature and pressure present a difficult technological challenge to traditional seismology. In recent years, balloon-based seismology through the study of low-frequency seismo-acoustic signals (infrasound) has gained acceptance as a viable way to study seismic activity on Venus. Balloon-based barometers have the potential to detect and characterize atmospheric waves launched by venusquakes and volcanic eruptions while offering substantially longer instrument lifetimes in the Venus middle atmosphere, where temperature and pressure are significantly more benign (0-100C, ~1 atm) as compared to the surface (> 460C, ~90 atm). A balloon-based investigation of Venus quake and volcanic activity can also serve as a pathfinder for highly-targeted missions involving long-lived surface seismometers in the future. In addition, auxiliary data collected to discriminate seismic infrasound from other naturally occurring sources can contribute valuable in-situ data to study important atmospheric science questions on Venus. Our activities are aimed at building a catalog of terrestrial balloon-recorded infrasound signals of geophysical provenance, using which signal predictions can be extended to Venus and the detectability of events can be analyzed. In this presentation, we will showcase highlights from the last year and discuss progress achieved towards the goal of balloon-based seismo-acoustic remote sensing on Venus. The last year produced one of the most consequential results of our effort the first detection of an earthquake from a balloon, shortly after the Ridgecrest earthquakes of 2019 in California. In addition, we successfully completed the first summer campaign of balloon overflights of the seismogenic zone in Oklahoma several times a week. We will share results and data analysis from the Ridgecrest and Oklahoma balloon campaigns. Finally, we will share our preparations for long-duration (up to 3 months) flight of infrasound sensors at 18-20 km altitude aboard the Strateole-2 mission, sponsored by the NSF (USA), CNES and LMD (France), to collect data on Earths infrasound background and geophysical infrasound signals of opportunity.