The surface of Venus shows evidence that the plates that make up its crust are moving in the form of crustal blocks that have jostled against each other like broken chunks of pack ice, new research suggests.
The movement of these blocks could indicate Earth’s neighbouring planet is still geologically active and gives scientists insight into both exoplanet tectonics and the earliest tectonic activity on Earth.
Researchers say the finding is important because it has long been assumed that Venus has an immobile solid outer shell, or lithosphere, just like Mars or Earth’s moon.
In contrast, Earth’s lithosphere is broken into tectonic plates, which slide against, apart from, and underneath each other on top of a hot, weaker mantle layer.
Paul Byrne, associate professor of planetary science at North Carolina State University and lead and co-corresponding author of the work, said: “We’ve identified a previously unrecognised pattern of tectonic deformation on Venus, one that is driven by interior motion just like on Earth.
“Although different from the tectonics we currently see on Earth, it is still evidence of interior motion being expressed at the planet’s surface.”
Researchers used radar images from Nasa’s Magellan mission to map the surface of Venus.
When analysing Venusian lowlands that make up most of the planet surface, they saw areas where large blocks of the lithosphere seem to have moved – pulling apart, pushing together, rotating and sliding past each other like broken pack ice over a frozen lake.
A computer model of this deformation, found that sluggish motion of the planet’s interior can account for the style of tectonics seen at the surface.
Prof Byrne said: “These observations tell us that interior motion is driving surface deformation on Venus, in a similar way to what happens on Earth.
“Plate tectonics on Earth are driven by convection in the mantle.
“The mantle is hot or cold in different places, it moves, and some of that motion transfers to Earth’s surface in the form of plate movement.
“A variation on that theme seems to be playing out on Venus as well.
“It’s not plate tectonics like on Earth – there aren’t huge mountain ranges being created here, or giant subduction systems – but it is evidence of deformation due to interior mantle flow, which hasn’t been demonstrated on a global scale before.”
Researchers say the deformation associated with these crustal blocks could also indicate Venus is still geologically active.
They are optimistic the planet’s newly recognised “pack ice” pattern could offer clues to understanding tectonic deformation on planets outside of our solar system, as well as on a much younger Earth.
The findings are published in Proceedings of the National Academy of Sciences.