🛰️ A massive tunnel beneath the surface of Venus

Beneath the opaque clouds of Venus, our sister planet, gigantic lava tunnels await exploration. Researchers have indeed announced they have identified an exceptional underground cavity proving the existence of these structures.

A team from the University of Trento has presented convincing evidence of an empty lava tube beneath the Venusian surface. This work, published in Nature Communications, uses radar data collected several decades ago. The identification of such a formation confirms that volcanism played a major role in the geological history of this planet.


To observe the surface of Venus, scientists must pierce its dense and permanent atmosphere. To do this, they use radar instruments, like the one on board NASA's Magellan probe in the 1990s. These waves penetrate the clouds and allow for surface mapping, while also detecting certain hidden formations. This is how an area of localized subsidence caught the researchers' attention.

The meticulous analysis of the images revealed an underground conduit of impressive size. According to estimates, this tube would have a diameter of about one kilometer (0.62 miles) and would extend for tens of kilometers. Its roof is at least 150 meters (about 492 feet) thick, and the empty cavity below reaches a depth of at least 375 meters (about 1,230 feet). These dimensions far exceed those of comparable structures on Earth or Mars.


The extreme conditions on Venus could explain the formation of these monumental structures. The dense atmosphere allows molten lava to quickly develop an insulating crust. This protection helps maintain large underground channels while magma continues to flow at depth. Consequently, the Venusian volcanic landscape could host extensive networks in the form of long tunnels.

This observation sets the stage for the next space missions dedicated to Venus. Projects like the European Space Agency's Envision and NASA's Veritas will carry more powerful radars. These instruments will produce higher-resolution images and will be able to probe the subsurface to depths of several hundred meters, searching for other cavities even without visible openings on the surface.


The presence of lava tubes on Venus refines our understanding of its geological evolution. These formations testify to intense volcanic activity in the past, and perhaps even recently. Future studies will attempt to map these hidden networks and assess their role in modifying the planet's surface. Each new piece of data thus offers an additional piece to the puzzle of Venusian history.

The formation and evolution of lava tubes

Lava tubes are created when molten lava flows from a volcano and begins to cool on the surface. The external part hardens rapidly, forming a solid crust, while the liquid magma continues to flow beneath. Over time, if the flow stops, the internal lava can drain away, leaving behind an empty or partially filled tunnel.

On Earth, these structures are modest in size, but on other planets, conditions can favor larger dimensions. For example, reduced gravity, as on Mars or the Moon, allows lava to spread more easily without collapsing. A dense atmosphere can also help retain heat and accelerate the formation of a protective crust.

A lava tube can remain stable for millennia if the roof is thick enough. Sometimes, sections of the roof collapse, creating openings called 'skylights' or access pits. These weak points are spotted from orbit and serve as clues for locating underground tunnels, as was the case on Venus.

Studying these tubes on different planets allows geologists to compare volcanic processes. This contributes to reconstructing the thermal and geological history of each world, illustrating how magma shaped landscapes over time. Furthermore, these cavities could one day offer natural shelters for human or robotic exploration, notably on Mars.