For decades, the surface of Venus has been hidden beneath a dense, opaque cloud cover. Now, scientists have announced a groundbreaking discovery: the confirmation of the planet’s first known subsurface cave, a lava tube. The finding, based on a reanalysis of data collected between and by NASA’s Magellan spacecraft, represents a pivotal moment in Venus exploration, demonstrating for the first time the existence of a void beneath the planet’s surface.
The study, led by researchers at the University of Trento in Italy, with funding from the Italian Space Agency (ASI), was published on , in the journal Nature Communications. The team successfully identified and characterized an underground structure formed by lava flows that solidified externally, leaving a hollow conduit – a phenomenon already observed on Earth, the Moon, and Mars, but previously only hypothesized on Venus.
The analysis focused on the volcanic region of Nyx Mons, where radar imagery indicated a localized collapse on the surface. According to Lorenzo Bruzzone, a co-author of the research and director of the Remote Sensing Laboratory at the University of Trento, advanced imaging techniques allowed the reconstruction of the subsurface conduit’s geometry from this visible depression. “The identification of a volcanic cavity is of particular importance because it allows us to validate theories that for many years were only hypotheses,” Bruzzone stated.
The results indicate a lava tube nearly one kilometer in diameter, with a roof at least 150 meters thick and an internal void no less than 375 meters deep. These dimensions place the structure among the largest ever identified in the solar system, exceeding most terrestrial tubes and approaching the upper limit predicted for lunar formations.
Venus’s physical conditions help explain this scale. Lower gravity compared to Earth and an extremely dense atmosphere favor the rapid formation of a solid crust over lava, allowing molten material to flow beneath and create wider, more stable conduits. The presence of such a structure reinforces the idea that the planet had, and possibly still has, intense and prolonged volcanic activity.
Lava tubes form within basaltic lava flows, where low-density lava continues to move beneath a solidifying surface, Bruzzone explained. This can happen in several ways: a solid crust may gradually grow inward from the edges of a lava channel, lava overflows can build up the channel’s levees until they form a roof, or floating fragments of cooled lava can merge and solidify into a continuous ceiling.
While the data currently confirms only the portion near the visible skylight, the terrain’s morphology and the existence of other similar depressions support the hypothesis that the subsurface system could extend up to 45 kilometers. Confirmation of this extension will depend on new observations, planned for missions like Envision, from the European Space Agency (ESA), and Veritas, from NASA, both equipped with radars capable of probing the Venusian subsurface with greater precision.
The discovery was made possible by applying a new technique to data collected by Magellan’s Synthetic Aperture Radar (SAR) instrument. Magellan mapped approximately 98 percent of Venus’s surface during its four-year mission from to , transmitting radio waves towards the surface and measuring the time it takes for them to bounce back. This allows for the creation of detailed radar images, even through the planet’s dense atmosphere.
Beyond deepening our understanding of Venus’s geological evolution, the discovery redefines the possibilities for researching one of the solar system’s most enigmatic planets. “This result opens new perspectives for the study of the planet,” Bruzzone summarized. Beneath a permanently cloudy sky, Venus is finally beginning to reveal what it hides in its depths.
The identification of this lava tube is significant not just for its size, but also for its potential implications for future exploration. Lava tubes offer potential shelter from the harsh conditions on Venus’s surface – extreme temperatures and crushing atmospheric pressure. While the current discovery doesn’t immediately suggest habitability, the existence of these subsurface structures raises the possibility that more temperate and protected environments might exist deeper within the planet’s crust.
The Magellan mission, despite being long-defunct, continues to yield valuable insights. This latest finding demonstrates the enduring power of archived data and the potential for new discoveries through innovative analysis techniques. It also underscores the importance of continued investment in planetary exploration and the development of advanced radar technologies for probing the hidden worlds of our solar system.
