Understanding Venus' interior structure is critical to determine its origin and evolution and explain why conditions on this planet are so drastically different from Earth. On Earth, seismic waves from earthquakes, recorded by seismometers, reveal our planet down to its core. Deploying seismometers on Venus is far more challenging due to extreme surface conditions (over 460°C and pressures near 90 atmos.). In contrast, conditions are much more favorable higher in the atmosphere (50–60 km altitude), where they resemble Earth. Could seismometers be deployed there to sense seismic waves? The answer is yes. Like a drum producing sound, Earth’s surface generates inaudible acoustic waves, called infrasound, during quakes. Yet, very few seismic events have been detected from balloons, and their potential remains largely unexplored.
In AIR’s second year, we explored the feasibility of using cutting-edge technologies to detect venusquakes and volcanic activity. Two techniques show promise: balloon-borne seismology and airglow cameras sensing upper-atmosphere light disturbed by acoustic waves. We demonstrated that a six-month balloon mission should allow at least one clear detection, while spaceborne airglow cameras could provide complementary observations. While tectonic seismicity is the most likely to be detected, we also studied volcanic eruptions. Simulations identified regions where atmospheric conditions favor long-range balloon detections of eruptions, challenging previous assumptions. With balloon data, we further showed that a planet’s interior can be constrained using only acoustic quake signatures.
Our work combines seismic hazard frameworks, large-scale simulations of seismic and acoustic waves, geochemical models, and geodynamic studies of planetary evolution.
Can we detect Venus seismicity?
We investigated both balloon detection capabilities and how airglow cameras could improve seismic observations. We computed the probability of detecting venusquake signals above noise thresholds over different observation times. Small signals are buried in turbulence or camera noise, but longer missions improve detection odds. Decade-long flights are impossible, but six-month balloon campaigns complemented by orbiting cameras appear feasible. Our results show tectonic activity is more detectable than volcanic.
Can we detect volcanic activity?
Recent evidence confirms Venus is volcanically active. Eruptions generate strong acoustic waves in both atmosphere and ground, which balloons could capture to reveal underground processes and source locations. Our modeling of surface sources identified new wave paths reaching 60 km altitude, broadening detection prospects.
Can we determine interior properties with sound waves?
We developed a probabilistic inversion model to retrieve quake sources and Venus’ interior properties from acoustic signatures. Tested on infrasound from the 2021 Mw7.1 Flores Sea earthquake, the method retrieved crust and mantle properties consistent with seismic velocity models. The resulting models showed uncertainties low enough to discriminate between different Venus evolution scenarios using only a sparse balloon network—a milestone proving the viability of balloon-based seismology.
Community and next steps
Through AIR, we aim to unite Venus, seismology, and infrasound communities in preparing future missions. We joined the VIVA proposal team to ESA as work package leaders for airglow cameras and contributed to the high-altitude acoustics and balloon workshop led by Daniel Bowman (PNNL), following our 2024 AIR workshop. Our results have gained attention at international conferences and are under review in journals.
With strong progress on detectability and inversion, our next focus is robustness: assessing how much information airglow data can provide and how Venus’ unique geology and atmosphere will affect seismic and acoustic wave propagation.
Our understanding of Earth's internal structure comes primarily from seismic waves that provide important constraints on subsurface seismic-velocity properties. However, traditional inversion methods cannot be implemented in regions of limited seismic-station coverage, in particular on Venus due to its harsh surface conditions but also in remote Earth regions. This lack of seismic data greatly limits our understanding of Venus’ origin and evolution, but also of the Earth’s subsurface. However, the mechanical coupling between the ground and its atmosphere enables the seismic energy to be transmitted into the atmosphere as low-frequency acoustic waves carrying information about the seismic source and the subsurface properties. While infrasound is traditionally recorded at ground-based stations, which suffers from the same in-situ deployment limitations as seismic stations, recent studies have demonstrated that balloon platforms can be used to monitor seismic activity from the atmosphere at a low operational cost. Balloon-borne seismology is a new dynamic field considered to be the only way to investigate Venus' interior. However, inversion of balloon-borne infrasound data has never been reported in the literature as field data are lacking and the coupling between seismic and acoustic waves in realistic media is poorly understood. Taking advantage of balloon pressure data collected by the Jet propulsion Laboratory and the Swedish Institute of Space Physics during large-scale balloon campaigns, the current project will address these key theoretical and practical issues by analyzing and modeling these seismically-induced infrasound signatures to retrieve the source and subsurface properties. AIR will first process and model the seismo-acoustic waves to analyze the field data. Results will then be injected in a statistical Bayesian inversion framework to retrieve uncertainties on source and subsurface properties and field-data processing from balloon campaigns.
