A new study has revealed that tectonic activity on Venus may have caused sections of the planet's upper crust to become fragmented into smaller bodies that, over vast swathes of time, barge past each other like chunks of pack ice on a body of water. The research hints that the tortured alien world – which is often described as Earth’s twin – may still be capable of hosting tectonic activity to this day.
As far as we know, Earth is unique in our solar system as the only planet to host plate tectonic activity. The vast plates that form Earth’s outer shell (which is also known as the lithosphere) are constantly on the move. Their motion is driven by changes in temperature that take place in the molten layer of rock that exists beneath the lithosphere.
Meanwhile, the planet Venus – despite sharing many key characteristics with our home world such as its size, density and surface composition – appears to lack this dynamic geological system. Instead, many members of the scientific community believe that the planet plays host to a solid shell-like lithosphere, as is the case with Earth’s moon.
The newly published study has challenged this belief, by identifying a previously unknown pattern of tectonic surface deformation on Venus. This pattern suggests the planet does not host a global solid shell as was previously believed, and that activity could even be continuing to this day.
The international team of researchers behind the paper created a surface map of Venus from images captured by NASA’s Magellan spacecraft. Magellan arrived in orbit around Venus on August 10, 1990, and spent the next four years and two months imaging the Venusian surface before ending its mission by undertaking a controlled plunge into the alien world’s atmosphere.
Upon analyzing the newly created map, the team discovered large blocks of land in the lowland regions of the planet. These appeared to have moved relative to one another in the recent geological past, in the same way that broken ice shifts atop a semi-frozen lake.
The researchers then used gravitational data on Venus (collected by the Magellan spacecraft) to create a computer model of the underground processes that could be driving the surface movement. It was found that shifts in the molten interior of the planet may account for the block land movement observed on the outer crust.
"These observations tell us that interior motion is driving surface deformation on Venus, in a similar way to what happens on Earth," comments North Carolina State University's Assoc. Prof. Paul Byrne, lead author of the new study. "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."
According to the authors, their work represents the first time that evidence of surface deformation due to interior mantle flow has been demonstrated on a global scale. Furthermore, the movement may have occurred relatively recently – in geological terms, at least. Potentially as recently as 150 million years ago in some regions, vast swathes of the Venusian surface were covered in lava flows that effectively resurfaced much of the planet.
"But several of the jostling blocks have formed in and deformed these young lava plains, which means that the lithosphere fragmented after those plains were laid down," explained Byrne. "This gives us reason to think that some of these blocks may have moved geologically very recently – perhaps even up to today."
The research is also helping to shed light on different forms of tectonic movement that could be occurring on distant exoplanets, and also the dynamics of ancient Earth, which may have hosted a lithosphere similar to that of modern-day Venus.
In the coming decade, Venus is set to be the focus of NASA’s VERITAS and DAVINCI+ spacecraft, as well as ESA’s Envision probe. Together these missions will revolutionize humanity’s understanding of the planet, and their high-resolution imagery could help test the team’s theory on recent tectonic movement.
The paper has been published in the journal Proceedings of the National Academy of Sciences.
