Venus’ surface is not a single, solid “lithosphere”, as once thought, but a patchwork of tectonic plates with similar activity to – but not the same as – those here on Earth, according to a new study out today in Proceedings of the National Academy of Sciences.
The study shows that these tectonic plates jostle and bump against one another like pack ice on a frozen lake, suggesting Venus is still geologically active.
“We’ve identified a previously unrecognised pattern of tectonic deformation on Venus, one that is driven by interior motion just like on Earth,” says Paul Byrne, associate professor of planetary science at North Carolina State University, the lead and co-corresponding author of the work. “Although different from the tectonics we currently see on Earth, it is still evidence of interior motion being expressed at the planet’s surface.”
Byrne and an international team of researchers used radar images from NASA’s Magellan spacecraft, which imaged the entire surface of Venus before plunging into the Venusian atmosphere in the summer of 1993 and breaking apart. Looking at the extensive Venusian lowlands, the team saw areas where large blocks of the lithosphere appeared to have moved, some pulling apart, others pushing together, and others sliding past one another.
By creating a computer model of this deformation, the team found that sluggish motion in the planet’s interior explains the more gentle tectonic activity occurring on Venus – as opposed to the violent tectonic motions on Earth, which can create huge mountain ranges or vast subduction systems.
The find is significant because Venus was once thought to have a motionless, solid surface just like Mars or the Moon, rather than a geologically active, moving surface.
“We know that much of Venus has been volcanically resurfaced over time, so some parts of the planet might be really young, geologically speaking,” Byrne says. “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. This gives us reason to think that some of these blocks may have moved geologically very recently – perhaps even up to today.”
The new “pack ice” pattern identified on our furnace-hot neighbour may offer clues about the deformation of tectonic plates on planets outside the solar system, as well as the geological formation of early Earth.
“The thickness of a planet’s lithosphere depends mainly upon how hot it is, both in the interior and on the surface,” Byrne says. “Heat flow from the young Earth’s interior was up to three times greater than it is now, so its lithosphere may have been similar to what we see on Venus today: not thick enough to form plates that subduct, but thick enough to have fragmented into blocks that pushed, pulled, and jostled.”
The new study is part of a renaissance in interest surrounding our neighbouring planet. Both NASA and the European Space Agency recently approved three new missions to Venus that will observe the planet’s surface and assess whether it once held oceans – and potentially life.
“It’s great to see renewed interest in the exploration of Venus, and I’m particularly excited that these missions will be able to test our key finding that the planet’s lowlands have fragmented into jostling crustal blocks,” Byrne says.
Amalyah Hart is a science journalist based in Melbourne.
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