Discovery of a hidden Lava tunnel beneath Venus

 Scientists for the first time discover the existence of a giant volcanic cave on Venus             

For the first time, scientists have strong evidence that a huge volcanic cave lies beneath the surface of Venus. Venus skylight in the Nyx Mons region reveals a subsurface cave, hypothesized to be a lava tube. The feature was identified through analysis of radar images acquired by the SAR instrument aboard the NASA Magellan mission. Scientists have uncovered evidence of a gigantic empty lava tunnel beneath Venus, revealing a hidden volcanic world on Earth’s mysterious twin. Volcanic landscapes are not limited to Earth. Scientists have previously identified signs of volcanic activity, including lava tubes, on Mars and the Moon. Now, researchers at the University of Trento have found compelling evidence that Venus also contains an empty lava tube beneath its surface. This finding adds to growing evidence that volcanism has played a major role in shaping Venus’s surface and geological history. By reanalyzing radar images from NASA’s Magellan mission, a team has identified what appears to be a giant lava tube under the volcano Nyx Mons. 

The underground structure was detected through the analysis of radar data as part of a research project funded by the Italian Space Agency. Because Venus is wrapped in thick clouds, standard cameras cannot see the surface. Magellan used Synthetic Aperture Radar in the early 1990s to build a global map instead. Those radar data are now paying off again. Using techniques first tested on lava tubes on the Moon and on Earth, the Italian team treated the radar image like an X-ray of the terrain. By measuring the length of the radar brightening inside pit A and the size of the shadow it casts, they could estimate the shape of the hidden void. The work, published in the journal Nature Communications, marks the first direct radar evidence of a subsurface conduit on our neighboring world. The newly described structure sits on the western flank of Nyx Mons, a shield volcano about 362 km's wide. In radar images, the key feature looks like a dark pit surrounded by a chain of similar collapses. The researchers call this standout depression “pit A. On most pits, the radar signal paints a simple picture of a steep hole. Pit A behaves differently. Its radar echo includes a bright, asymmetric streak which stretches well beyond the rim. According to the team, the pattern matches what is seen when radar waves enter a skylight, bounce along an underground tunnel and then scatter back to the spacecraft sensors. In other words, pit A is probably a skylight, the collapsed roof of a lava tube that once carried molten rock beneath the surface.

From 1990 to 1992, NASA’s Magellan spacecraft mapped Venus using a Synthetic Aperture Radar system. The research team examined Magellan’s radar images in areas showing signs of localized surface collapse. Using an imaging technique they developed to identify underground conduits near skylights, they detected a large subsurface structure in the Nyx Mons region. "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. We interpret the structure as a possible lava tube (pyroduct), with an estimated diameter of approximately one km, a roof thickness of at least 150 meters, and an empty void deep of no less than 375 meters,” says Bruzzone. Magellan’s Radar System displayed several pit chains and the identified skylight, marked as A, potentially providing access to the subsurface. The results point to an enormous conduit. The tube is roughly 1 km wide on average, with a roof at least 150 meters thick and an empty space below which is no less than about 375 meters high. Radar echoes show the signal traveling inside the tube for at least 300 meters from the skylight. Based on the alignment of nearby pits and the slope of the surrounding terrain, the full system may extend for around 45 km beneath Nyx Mons. For comparison, famous lava tubes on Earth such as Cueva de los Verdes on Lanzarote reach widths of only a few tens of meters. The Venusian tube dwarfs them.

“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. Lava tubes are more than geological curiosities. They preserve a record of how a planet’s volcanoes erupted and cooled over time. On Mars and the Moon, they are also seen as potential natural shelters for future explorers, since solid rock walls can block harmful radiation and micrometeorites. On Venus, with surface temperatures above 450 degrees Celsius and pressures more than ninety times higher than on Earth, no one is setting up camp inside Nyx Mons any time soon. Still, the discovery is a big deal. Venus is often described as Earth’s twin which took a very different path, ending up with a runaway greenhouse atmosphere rich in CO2 and clouds of sulfuric acid. Understanding how its volcanoes work helps researchers piece together how the planet lost any past oceans and became the extreme world we see today. Volcanic plumbing ties directly into how gas moves between the interior and the atmosphere, which is central to long-term climate evolution.

Conditions on Venus may actually favor the formation of unusually large lava tubes. The planet’s lower gravity and dense atmosphere could allow molten lava to quickly develop a thick, insulating crust once it flows away from a volcanic vent. This crust would help preserve large underground channels as lava continues to move beneath the surface. The lava tube identified by the researchers appears to be both wider and taller than lava tubes found on Earth or those predicted for Mars. Its size places it at the upper end of what scientists have proposed, and in one instance observed, on the Moon. This scale is consistent with other volcanic features on Venus, including lava channels which are longer and larger than those seen on other rocky planets. There is also a practical angle. Radar data show that lava channels and collapse chains are common on Venus. If one lava tube this large can hide in thirty year old images, many more may be waiting in the archives and on the surface. That is why the team stresses that their analysis is probably just scratching the surface. Locating lava tubes on other planets is extremely challenging. Because these structures form underground, they typically remain hidden from view. They are usually discovered only when a section of the roof collapses, leaving a pit which can be seen at the surface. These surface openings can point to the presence of a lava tube and may also indicate a possible entrance.

On Venus, the task is even more difficult. Thick clouds permanently blanket the planet, blocking direct observation with traditional cameras. As a result, scientists must rely on radar imaging to study the surface and what lies beneath it. Future orbiters will be able to check this candidate cave in far more detail. The European Space Agency’s planned EnVision mission and NASA VERITAS will both carry new radar instruments with resolutions down to a few tens of meters. One of them, EnVision’s Subsurface Radar Sounder, is designed to send radio waves a few hundred meters below the surface, exactly the depth of the Nyx Mons tube. In practical terms, this means upcoming spacecraft could not only confirm the size of this cavern near pit A but also map intact lava tubes that show no surface collapses at all. Step by step, scientists would get a three-dimensional picture of Venusian volcanic systems, something that has never been possible before. “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 km's,” Bruzzone explains. “Our discovery therefore represents only the beginning of a long and fascinating research activity,” he concludes. “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.”

For people following climate news on Earth, this kind of planetary geology might seem far away from the daily worry about energy use or the electric bill. Yet Venus offers a sobering example of how a rocky world with roughly Earth’s size can end up with crushing air pressure and oven-like temperatures when greenhouse gases dominate the atmosphere. The more we learn about its volcanoes and buried tunnels, the better we can understand how planets tip from habitable to hostile. Both missions will carry advanced radar instruments designed to produce sharper surface images, allowing scientists to analyze small pits in far greater detail. Envision will also include an orbital ground penetrating radar (Subsurface Radar Sounder) capable of probing several hundred meters below the surface and potentially detecting underground conduits even when no surface openings are visible.