Venus and Earth are sometimes called twins because they’re pretty much about the same size. They also formed in the same inner part of the solar system, out of the same materials. Venus is in fact our closest neighbor to Earth. So, you would think that they would have turned out very, very similar.
Nope. Earth looks like paradise compared the hellscape that is Venus. In fact, it’s so hot on Venus that you can melt lead. The temperatures on the surface of Venus are over 900 degrees Fahrenheit (480 degrees Celsius), and the planet is covered in a 15-mile-thick layer of clouds. And those clouds are made of sulfuric acid. So, it is a really crazy place — and now it just got a lot more interesting.
In a new study, scientists have uncovered something new under its hellish surface: vast lava-carved tunnels that shouldn’t even exist there.
These are not modest cavities. They are some of the most enormous underground structures ever found in the solar system.
“Earth lava tubes have smaller volumes, Mars tubes have slightly bigger volumes, and then the Moon’s tubes have even bigger volumes — and then there’s Venus, completely disrupting this trend, displaying very, very big tube volumes,” Barbara De Toffoli of the University of Padova told the audience during the Europlanet Science Congress in Helsinki earlier this month.
Breaking the Rules of Planetary Geology
Lava tubes are familiar on Earth. They form when the surface of a lava flow hardens while molten rock continues to drain beneath, leaving behind a hollow conduit. On the Moon and Mars, weaker gravity lets them sprawl even larger. Scientists thought that rule of thumb — less gravity, bigger tubes — was universal. Venus just broke it.
Venus has nearly the same gravity as Earth. Its tubes should be modest, not Moon-sized. But De Toffoli’s team found the opposite. By combining radar imagery and mapping data from past missions, they identified four sinuous pit chains near giant shield volcanoes. These pits lined up with volcanic slopes, exactly where lava would have flowed. Their depth-to-width ratios matched those of collapsed lava tubes, not tectonic fractures.
The sheer scale floored the researchers. Volumes inferred from the collapsed pits rival those of lunar tubes, suggesting Venus may host some of the largest subsurface cavities in the solar system. “This is already giving away the fact that there’s likely something more on Venus playing a significant role,” De Toffoli said.
What Could Be Making These Cavities So Big?
One explanation could be Venus’s extreme environment. With crushing surface pressures and temperatures hot enough to melt lead, lava may behave differently than anywhere else. De Toffoli suggested that “due to the very high pressure, there’s an overall flattening out of the tubes, instead of having a very intense erosion at the floor that usually happens on other planets,” according to New Scientist.
That would mean Venusian lava tubes are not just anomalies — they are windows into how volcanism adapts under alien physics. They could also help explain how the planet’s surface transformed into a volcanic wasteland.
The discovery comes with practical stakes too. On the Moon and Mars, space agencies eye lava tubes as natural bunkers for future astronauts. On Venus, where surface missions fry in hours, such cavities could someday be targets for robotic explorers or even imagined refuges in the distant future.
For now, the evidence comes only from orbital radar. To really see these tunnels, we’ll need sharper eyes. The European Space Agency’s EnVision mission, slated to launch in 2031, carries a Subsurface Radar Sounder designed to peer hundreds of meters below Venus’s crust. De Toffoli’s team says it could finally map these alien catacombs.
Billions of years ago, Venus may have had oceans. If that’s true, these giant cavities might preserve chemical traces of that lost water world. They could also reveal whether volcanism played a role in turning Venus into the runaway greenhouse we see today.
Venus has more volcanoes than any other planet. And now, it also has the strangest underground tunnels we’ve ever found. As De Toffoli and colleagues conclude in their paper: “The characteristics of the observed Venusian lava tubes, particularly their large scale, suggest that Venus may host some of the most extensive subsurface cavities in the solar system.”
