For the first time, scientists have strong evidence that a huge volcanic cave lies beneath the surface of Venus. By reanalyzing radar images from NASA’s Magellan mission, a team from University of Trento has identified what appears to be a giant lava tube under the volcano Nyx Mons. The work, published in the journal Nature Communications, marks the first direct radar evidence of a subsurface conduit on our neighboring world.
A hidden cave beneath Nyx Mons
The newly described structure sits on the western flank of Nyx Mons, a shield volcano about 362 kilometers 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 that stretches well beyond the rim. According to the team, that 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.
Reading a cave from radar echoes
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.
Their results point to an enormous conduit. The tube is roughly 1 kilometer wide on average, with a roof at least 150 meters thick and an empty space below that 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 kilometers 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.
Why lava tubes on Venus matter
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 that took a very different path, ending up with a runaway greenhouse atmosphere rich in carbon dioxide 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.
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.
A target for the next generation of Venus missions
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, that 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.
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.
The study was published in Nature Communications.
