For the first time, scientists have strong evidence that there is a large volcanic crater beneath the surface of Venus. By reanalyzing radar images from NASA’s Magellan mission, a team from the University of Trento has identified what appears to be a large lava flow beneath the Nyx Mons volcano. Work, published in a newspaper Nature Communicationmarks the first direct evidence of an underground fiber radar in our neighborhood.
A hidden cave beneath Nyx Mons
The newly described structure is located on the western side of Nyx Mons, a volcano that is 362 kilometers long. In radar images, the main part looks like a dark hole surrounded by a chain of similar collapses. Researchers call this prominent emotional stress “pit A”.
In most holes, the radar signal creates a simple image of the slope. Pit A behaves differently. Its radar echo consists of a bright, irregular streak extending beyond the edge. According to the team, that pattern is consistent with what is seen when radar waves enter the sky, hit an underground tunnel and then scatter back to the spacecraft’s sensors.
In other words, crater A is probably a skylight, the collapsed roof of a lava tube that once sent molten rock beneath the surface.
Cave reading from radar echoes
Because Venus is covered in thick clouds, conventional cameras cannot see the surface. Magellan used Synthetic Aperture Radar in the early 1990s to map the world. Those radar points are paying off again.
Using techniques that were first tested on lava tubes on the Moon and on Earth, the Italian team captured a radar image like an X-ray of the area. By measuring the length of the radar beam into hole A and the size of the shadow it cast, they could estimate the shape of the hidden hole.
Their results indicate a large tunnel. On average, the tube is 1 kilometer wide, has a roof of at least 150 meters and an empty space below the height of 375 meters. Radar echoes show a signal traveling through the tube at least 300 meters from the skylight. Based on the sequence of craters and the slope of the surrounding terrain, the entire system may extend as much as 45 kilometers beneath Nyx Mons.
In comparison, the world’s most famous lava tubes such as Cueva de los Verdes in Lanzarote are only a few tens of meters wide. Venusian tubes weaken them.
Why the lava tubes on Venus are important
Lava tubes are more than geological wonders. They keep track of how the planet’s volcanoes have erupted and cooled over time. On Mars and the Moon, they are also considered natural habitats for future explorers, as solid rock walls can block radiation and micrometeorites.
On Venus, with temperatures above 450 degrees Celsius and pressures more than ninety times higher than on Earth, no one will be camping inside Nyx Mons anytime soon.
However, discovery is a big deal. Venus is often described as Earth’s twin that took a very different path, ending up in a seething greenhouse atmosphere rich in carbon dioxide and sulfuric acid clouds.
Understanding how volcanoes work helps researchers piece together how the planet lost any oceans in the past and became the extreme world we see today. Volcanic plumes are directly linked to the flow of gas between the atmosphere and the atmosphere, which is central to long-term climate change.
There is also a working corner. Radar data shows that lava channels and collapse chains are common on Venus. If one lava tube this large can be hidden in thirty-year-old photos, many more may be waiting in the archives and above. That’s why the team stresses that their analysis may only scratch the surface.
The goal of the next generation of Venus missions
Future orbiters will be able to explore this candidate cave in detail. The European Space Agency’s proposed EnVision mission and NASA VERITAS will both deploy 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 fact, that means that a future spacecraft would not only confirm the size of this cave near crater A but also map the lava tubes that show no collapsing surface at all. Step by step, scientists would obtain a three-dimensional picture of the Venusian volcanic processes, something never before possible.
For people who follow the weather on Earth, this type of planetary geology may seem far removed from everyday concerns about energy use or electricity bills. Yet Venus provides a stark example of how a rocky, Earth-sized planet can end up with high atmospheric pressure and oven-like temperatures as greenhouse gases dominate the atmosphere.
The more we learn about volcanoes and trenches, the better we can understand how planets go from habitable to violent.
The lesson was published in Nature Communication.
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