Venus is often described as Earth’s sister planet. Both planets have similar size and densities, indicating somewhat similar core compositions. The primary difference between the two is orbital distance from the sun.
Venus, like Earth, is covered with geological features including volcanoes and mountains. We know how mountains formed on Earth – tectonic plates. Mountains are formed at the boundaries of tectonic plates as a result of the plates colliding and/or moving away from each other.
So on Venus, how were these mountains formed? It is commonly believed that Venus does not currently demonstrate plate tectonic activity. A possible explanation for the lack of observable plate tectonics is the planet’s proximity to the sun. The high surface temperature means it’s extremely unlikely that there is any remaining water in the crust of Venus. Water tends to soften and lubricate rock, which would allow the crust to fracture into plates (like on Earth).
But we have evidence that there should be (or should have been) plate tectonic activity. There are three “continents” on the surface of Venus. On Earth, the continents are a direct result of plate tectonics. The strong presence of volcanoes and lava flows strongly indicate tectonic activity under the surface, beneath a seemingly uniform crust. However, if there were currently active plate tectonics, we would expect the surface of Venus to look much more like Earth, with various ridges and trenches.
So how did these form? There are some impact craters on the surface, but those don’t account for the observed surface features. Were plate tectonics on Venus once an active cycle that’s now obsolete? So far, it remains something of a mystery. Future missions to investigate further are unlikely in the near future, because of the hostile atmosphere of Venus; any visiting spacecraft would likely never be recovered.
An extra fun thought: what would Earth look like without plate tectonics?