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Written by Paul K. Byrne, North Carolina State University on June 22, 2021
New research suggests that Venus’ crust is divided into large clumps – reddish and dark purple regions – that are surrounded by belts of tectonic structures outlined in bright yellow and red. Credit: North Carolina State University, based on original NASA/JPL images
The surface of Venus is cracking and moving like ice floating on the ocean – likely due to tectonic activity.
Big Idea الفكرة
Much of Venus’s fragile upper crust is splitting into bits that scramble and move—and the slow ripple of Venus’s mantle below the surface may be responsible. My colleagues and I made this discovery using decades-old radar data to explore how the surface of Venus interacts with the planet’s interior. We describe them in a new study published in the Proceedings of the National Academy of Sciences on June 21, 2021.
Planetary scientists like myself have known for a long time that Venus has a large number of tectonic terrains. Some of these formations are long, thin belts where the crust is pushed together to form burrs or torn to form troughs and grooves. In many of these belts, there is evidence that pieces of the crust have moved side by side as well.
Our new study shows, for the first time, that these bands of ridges and troughs often define the boundaries of flat and trough regions that themselves show relatively little deformation and are individual masses of Venus’ crust that have moved, rotated and slipped in the past. Over time – and they probably did in the recent past. They are somewhat similar to Earth’s tectonic plates but on a smaller scale and more like a pack of ice floating over the ocean.
Venus’ crust breaks into large pieces that behave more like chunks of ice floating on the ocean. Credit: Endlisnis/WikimediaCommons, CC BY
The researchers hypothesized – just like Earth’s mantle – that Venus’ mantle rotates with currents as it is heated from below. My colleagues and I engineered the slow but powerful motion of Venus’ mantle and showed that it was strong enough to break up the upper crust everywhere we found these low-lying land masses.
why does it matter
The main question about Venus is whether the planet has active volcanoes and tectonic faults today. It’s basically the same size, composition, and age as Earth – so why isn’t it geologically alive?
When pieces of ice collide, the ice is pushed up to create outcrops much like what researchers believe happens on Venus. Credit: Ben Holt and Susan Digby / Wikimedia Commons
But no mission to Venus has conclusively shown that the planet is active. There is tantalizing but ultimately inconclusive evidence that volcanic eruptions occurred there in the recent geological past – and may still be ongoing. The issue of tectonic activity – the creaking, cracking and folding of the planet’s crust – is on less solid ground.
Showing that the geological engine of Venus is still in operation will have huge implications for understanding the formation of the planet’s mantle, where and how volcanoes can occur today and how the crust itself is formed, destroyed and replaced. Since our study suggests that some of this crustal clash is geologically recent, we may have taken a huge step forward in understanding whether Venus is really active today.
The largest mass of lowlands the team found – the dark red shape in the center of this radar image – is the size of Alaska and is surrounded by edges and distortions that appear in lighter colors. Credit: Paul K. Byrne/NASA/USGS, CC BY-ND
What is still unknown
It is not clear how common these cortical fragments are. My colleagues and I have found 58 so far, but this is almost certainly a low estimate.
Nor do we yet know when these crustaceans first formed, nor how long they have been moving on Venus. Determining when crustal fragmentation and scramble occurred is key—especially if planetary scientists want to understand this phenomenon in connection with the planet’s recent suspected volcanic activity. Discovering this will give us vital information about how the surface features of the planet reflect the geological disturbances within.
What’s Next
This preliminary study allowed my colleagues and I to make our best guess yet about how the vast lowlands of Venus are deformed, but we need high-resolution radar images and topographic data to build on this work. Fortunately, that’s exactly what scientists will have in the coming years, as NASA and the European Space Agency recently announced new missions bound for Venus later this decade. It would be worth the wait to get a better understanding of Earth’s mysterious neighbor.
Written by Paul K. Byrne, Associate Professor of Planetary Science, North Carolina State University.
Originally published on The Conversation.
For more information on this research, see Revealing the geological secrets of Venus through “ice pack” tectonics.
Reference: “Globally Fragmented and Moving Lithium on Venus” by Paul K. Sciences. DOI: 10.1073/pnas.2025919118
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