Strange Geological Structures on Venus May Help Explain Inner-Workings of Earth

The surface of Venus is an inhospitable place. It is hot (over 400 degrees Celsius) and the air pressure in its hostile atmosphere is almost 100 times higher than on Earth. Due to its bowl-like structure primarily made of solid components, however, it is one of the four planets in our solar system that are most like Earth and thus of interest to science. Although Venus seems geologically “dead” nowadays, it is littered with scar-like, ring-shaped structures that bear testimony to a turbulent history and cannot be found on Earth. These unique structures are referred to as novae and coronae.

Two structures of the same origin?

Both structures, as astro and geophysicists suspect, stem from a period when Venus was geologically active and are supposed to have formed through volcanic and related tectonic processes. There is speculation that the entities were formed through an interplay between the rigid crust and convection currents in the mantle that transport hot rock material to the surface and carry cooled rock back down. However, it is unclear whether their formation is interconnected and one structure emerges from the other or they develop completely independently.

Based on computer simulations, Taras Gerya, a professor of geophysics at ETH Zurich, has now managed to recreate the striking surface structures for the first time and thus provide a plausible explanation for their formation. The results of his simulations have just been published in the journal Earth and Planetary Science Letters.

In his thermomechanical model, he simulated defined processes inside Venus for the first time in 3D. The simulations suggest that novae form first and coronae can develop from them over millions of years. Consequently, the geophysicist concludes that both structures may well stem from the same origin.

Evolution of a ring structure

So far, sixty-four novae measuring 100 to 300 kilometres in diameter have been identified on Venus. The ring-shaped structures in Venus’ crust are interspersed with star-shaped fracture zones that are formed through as yet unknown tectonic and magmatic processes.

Structural analyses have already revealed that novae can also form structures that are similar to those of coronae. In contrast to novae, these 513 structures are sometimes extremely complex: their outermost ring is raised. A trench separates them from another ring-shaped ridge, which leads into a depression before the central area of the structure stands out. Like the Artemis Corona, coronae can be up to 2,600 kilometres in diameter and contain a large number of small volcanoes.

According to Gerya, previous, exclusively two-dimensional models for the reconstruction of the entities originated from a lithosphere (crust and areas of the upper mantle) that was too cold, thick and rigid. However, the latest studies suggest that Venus’ lithosphere is relatively warm, thin and ductile, as the researcher writes. Moreover, such a lithosphere was recently discovered on Venus among seemingly active hotspots – volcanoes that are fed by hot mantle material. The hot rock material wells up in form of a large “mushroom” to the surface of the planet from the depths of the mantle. As long as it does not break the surface, it is referred as “mantle plume”. If plume-generated magma penetrates the crust, a hotspot forms where lava erupts.

Simulating“mantle plumes”