Evidence of a subsurface lava tube on Venus

Volcanic activity is not unique to Earth: traces of volcanic activity, such as lava tubes, have been found on Mars and the Moon. Now, the University of Trento has demonstrated the existence of an empty lava tube even in the depths of Venus, a planet whose surface and geology have been largely shaped by volcanic processes.

The cave was identified through radar data analysis as part of a project funded by the Italian Space Agency. The discovery was published by Nature Communications.

"Our knowledge of Venus is still limited, and until now we have never had the opportunity to directly observe processes occurring beneath the surface of Earth’s twin planet. The identification of a volcanic cavity is therefore of particular importance, as it allows us to validate theories that for many years have only hypothesized their existence," explains Lorenzo Bruzzone, the coordinator of the research, full professor of Telecommunications and head of the Remote Sensing Laboratory at the Department of Information Engineering and Computer Science of the University of Trento. "This discovery contributes to a deeper understanding of the processes that have shaped Venus’s evolution and opens new perspectives for the study of the planet," he adds.

Finding lava tubes outside the Earth is not easy. Because they form underground, these caves usually remain hidden and can only be spotted when part of their roof collapses, creating a pit visible on the planet’s surface. These collapses may reveal both the presence of a lava tube and a possible entrance to it. On Venus, the search is even more challenging, since the planet is covered by thick clouds that block direct views of the surface with standard cameras, forcing scientists to rely on radar images.

Between 1990 and 1992, a Synthetic Aperture Radar, an instrument aboard NASA's Magellan spacecraft, mapped the surface of Venus. "We analyzed Magellan's radar images where there are signs of localized surface collapses using an imaging technique that we have developed to detect and characterize underground conduits near skylights. Our analyses revealed the existence of a large subsurface conduit in the region of Nyx Mons, the area named after the Greek goddess of the night. We interpret the structure as a possible lava tube (pyroduct), with an estimated diameter of approximately one kilometer, a roof thickness of at least 150 meters and an empty void deep of no less than 375 meters," says Bruzzone.

The physical and atmospheric parameters of Venus could favor the formation of lava tubes. In fact, Venus has a lower gravity and a denser atmosphere than Earth, which would favor the rapid creation of a thick insulating crust immediately after the lava flow leaves the vent.

The lava tube that has been identified appears to be wider and taller than those seen on Earth or predicted for Mars. It falls at the upper end of what scientists have suggested (and in one case actually observed) on the Moon. This is not surprising, since Venus has lava channels that are larger and longer than those observed on other planets.

"The available data allow us to confirm and measure only the portion of the cavity close to the skylight. However, analysis of the morphology and elevation of the surrounding terrain, together with the presence of other pits similar with the one studied, supports the hypothesis that the subsurface conduits may extend for at least 45 kilometers. To test this hypothesis and identify additional lava tubes, new higher-resolution images and data acquired by radar systems capable of penetrating the surface will be required. The results of this study are therefore very important for future missions to Venus, such as the European Space Agency’s Envision and NASA’s Veritas. Both spacecraft will carry advanced radar systems capable of capturing higher-resolution images, allowing scientists to study small surface pits in greater detail. In addition, Envision will carry an orbital ground penetrating radar (Subsurface Radar Sounder) capable of probing Venus’s subsurface to depths of several hundred meters and potentially detecting conduits even in the absence of surface openings. Our discovery therefore represents only the beginning of a long and fascinating research activity," he concludes.

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