Researchers find evidence of tectonic activity on Venus

Old data also offers the opportunity for new insights: A new analysis of data collected by the Magellan probe from over 30 years ago has provided a team of astronomers with important insights into the planet Venus, according to the University of Bern.

For a long time, it was thought that there was no tectonic activity on Venus. According to a recent study published in the journal Science Advances, the surface of the planet is constantly being reshaped. However, this works differently to plate tectonics on Earth.

The feature that the team led by Anna Gülcher from the University of Bern was interested in is called a corona. A corona is a ring-shaped structure that can have a diameter of several tens to several hundred kilometers. There are around 740 of these structures on the planet.

The largest corona studied is 200 kilometers in size

“We focused on the 75 largest coronae, as these are the only ones where the gravity data is resolved well enough to study them in detail,” said Gülcher. The largest one the team studied is 2500 kilometers across.

Most coronae are located in regions where the planet's crust is thinner. It is assumed that bubbles of hot mantle material rise there and inflate the crust. This causes the edge of these regions to be pushed under the crust in many places, similar to plate tectonic subduction on Earth.

In about two thirds of the coronae, the researchers found disturbances in the planet's gravitational field – the gravity data were recorded by Magellan at the time. According to the researchers, these disturbances indicate the density of the lithosphere and are consistent with thermal upwelling currents of hot material rising from beneath the planet's crust.

The researchers have simulated the probable formation of the coronae on the computer: “It starts with material in the interior of Venus heating up,” explains Gülcher. “The heated material then rises through the Earth's mantle in a so-called plume, which is located under the coronae. This buoyancy creates a tectonic dynamic that leads to the peculiar shape.”

Material rises and lifts the surface

Closer to the surface, the rising material is melted. It lifts the surface of the corona and expands radially, increasing the diameter of the corona. If the material pushing outwards collides with the surrounding crust, a mountain ring is formed at the edge of the corona. Similar to plate tectonics on Earth, the colder crust can push under the warmer interior, creating faults and depressions that characteristically surround a corona.

The findings about coronae could also be a glimpse into Earth's early history: “Coronae don't exist on Earth today, but they may have existed when our planet was young and before plate tectonics formed,” said Gael Cascioli of the University of Maryland, the study's lead author. “By combining gravity and topography data, our research provides a new and important insight into the possible subsurface processes that are currently shaping the surface of Venus.”

The US probe Magellan was launched aboard a space shuttle on May 4, 1989, and reached Venus in August 1990. In the following years, the probe orbited the planet and mapped its surface using radar that penetrated its dense atmosphere. On October 12, 1994, Magellan burned up in the atmosphere of Venus.

The researchers need more data with a higher resolution to investigate the coronae further. However, this will probably not be available for several years: In the early 2030s, the European probe EnVision and the US probe Veritas are due to be launched, both of which will collect data on Venus' gravitational field, among other things.

(wpl)