Something is happening on Venus. The surface of our neighbouring planet, often considered dead and inactive, is covered in strange lines that denote some kind of active erosion.
These lines cover about 7 per cent of Venus’s surface and are called tesserae. They were spotted by the Russian Venera orbiters in the early 1980s and are characterised by long, parallel lines on hills and mountains that look like the ground has folded over itself.
Paul Byrne at North Carolina State University and his colleagues examined the few radar images that we have of Venus’s surface to try to figure out what these tesserae are. They notice that the lines tend to curve along features on the ground, similar to a topographical map, rather than simply cutting through everything.
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“If you imagine getting a phone book and then you take a chainsaw and carve topography into it, when you look down on that book that you’ve now butchered, you see this complicated curving pattern of those sheets of paper,” says Byrne. That curving pattern is similar to the pattern of the tesserae, and indicates that they must be made of some sort of layered rock.
It isn’t clear how these layers came to be, but Byrne and his colleagues suspect that some of them may be sheets of lava folded over themselves into stacks. Regardless of whether it is a stack of lava or simply a sedimentary rock, they found that something must be wearing down the surface to expose the sides of the layers.
“For us to see these lines in this curving pattern, there must be erosion,” says Byrne, who was in The Woodlands, Texas. “In the last few hundred million years, there has been wind planing off sediment and carving these weirdo terrains.”
There is no reason to think that Venus’s weather would have changed over that time, so those winds are probably still slowly wearing down the hills of Venus today.
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