Venus’s cracked surface behaves like sea ice

The Magellan spacecraft captured this radar view of Venus, showing the largest dark red tectonic block in the center, which is roughly the size of Alaska. The lighter colors around the block are warps and ridges. Image via NASA-JPL / Paul Byrne / NCSU.

Cracked surface of Venus

Venus is a rocky world similar in size and density to Earth. It is sometimes said to be the “twin” of the Earth. However, the surface of Venus is far from being terrestrial today. The planet surrounded by clouds is hot enough on its surface to melt lead. But scientists believe the surface of Venus looked more like Earth in the past. It could have had a more Earth-like atmosphere, and even surface water (like in ancient oceans). In late June 2021, researchers at North Carolina State University (NCSU) provided more evidence of an Earth-like Venus. This showed that Venus may have already been geologically active and could still be active today.

The new analysis showed that experiments on the surface of the planet ice floe tectonic. In other words, blocks of Venus’ crust – somewhat resembling ice floes on frozen lakes or the ocean – appear to be mobile.

It’s not quite the same as tectonic plates on our planet, where Earth’s large terrestrial plates move over time. But it’s similar. And, moreover, it is not a given that Venus has a mobile crust. Mars does not, for example. Neither does Earth’s moon.

Researchers published their new Peer reviewed discoveries in the Proceedings of the National Academy of Sciences (PNAS) on June 29, 2021.

Red blocks surrounded by many thin, lighter streaks.
New research suggests that Venus’ crust is divided into large blocks – the dark reddish-purple areas – which are surrounded by belts of tectonic structures depicted in a lighter yellow-red color. Image via The conversation/ Paul K. Byrne / NASA / USGS.

Ice floe and plate tectonics

The study found regions on the surface of Venus, in the lowlands where the crust is broken into blocks, which jostle against each other. This is how ice floes behave on Earth. As the main author Paul Byrne from North Carolina State University explained:

Our new study shows, for the first time, that these ridges and troughs often mark the boundaries of flat and low areas which themselves exhibit relatively little deformation. These are individual blocks of Venus’ crust that have moved, rotated, and slid over each other over time. And they may have done so in the recent past. It’s a bit like plate tectonics on Earth, but on a smaller scale and more like ice floes floating on top of the ocean.

Although these blocks are reminiscent of tectonic plates, there are differences. On Earth, tectonic plates collide, pull apart, or slide over each other. This occurs in the region called the lithosphere (the crust and the upper part of the mantle).

This collision and sliding also occurs on Venus. But the process does not create subduction zones (when two plates collide, the more dense plate is subjugated under the less dense plate) or mountain ranges.

Man in dark arctic costume standing in snow in front of stacked chunks of ice.
Where pieces of ice collide, the ice is pushed upward to create ridges much like what researchers think is happening on Venus. Image by Ben Holt and Susan Digby / WikimediaCommons.
Aerial view of white irregular leaves and pieces separated by fine dark waterways.
Venus’ crust is fractured into large chunks that behave more like chunks of ice floating on the ocean. Image via Endlisnis / WikimediaCommons.

A sign of inner activity

Movement on the surface gives an idea of ​​what might be happening below the surface. Byrne said:

It is not plate tectonics like on Earth – there are no huge mountain ranges being created here, or giant subduction systems – but it is evidence of due deformation. to the inner mantle flow, which has not been demonstrated globally before.

Yet the tectonics seen on Venus is the closest thing to Earth tectonics found anywhere else in the Inner Solar System so far. As described in the document:

These movements can be the result of convection of the mantle. If so, they are a style of interior-surface coupling that is not seen anywhere else in the Inner Solar System except for continental interiors on Earth. The mobile and fragmented lithosphere of Venus may provide a framework for understanding how tectonics on Earth worked in the Archean.

In other words, tectonic activity on Venus could be similar to what happened on Earth in ancient times, around 4 billion to 2.5 billion years ago.

Man in hiking gear with clouds and barren mountain behind him.
New research on tectonic processes on Venus was led by Paul Byrne at North Carolina State University. Image via NCSU.

Magellan Radar Charts of Venus

Researchers made the discovery using NASA radar images Magellan spacecraft, which was launched in 1989 and orbited Venus until 1994. They not only saw regions containing the blocks, but also that the blocks had moved. The movement looked like broken ice floes over frozen lakes on Earth. Byrne said:

These observations tell us that inner movement causes deformation of the surface on Venus, much like it does on Earth. Plate tectonics on Earth are driven by convection in the coat. The mantle is hot or cold in different places, it moves, and part of this movement is transferred to the Earth’s surface in the form of plate movement.

Bright and dark orange marbled surface of a planet on a black background.
This image is a composite of NASA data Magellan spaceship and Pioneer Venus Orbiter. New research shows that the surface of Venus is divided into blocks resembling ice floes on frozen lakes. Image via Nasa/ JPL-Caltech.

The type of tectonics observed seems to correlate with the inner gloom of the planet. The observed deformation suggests that Venus is still geologically active today, an exciting implication. Byrne continued:

Showing that Venus’ geological engine is still working would have huge implications for understanding the makeup of the planet’s mantle, where and how volcanism might take place today, and how the crust itself is formed, destroyed, and replaced. Because our study suggests that some of this crustal hustle and bustle is geologically recent, we may have taken a big step forward in understanding whether Venus is truly active today.

Color-coded map of the Earth divided into irregular sections of different sizes.
The surface of the Earth is divided into tectonic plates of different sizes (simplified map). The tectonic characteristics of Venus are somewhat similar, but on a smaller and less developed scale. Image via USGS / Wikipedia.

Tectonics on other worlds

Understanding the tectonic processes on Venus helps scientists determine what the planet looked like a few billion years ago and how it became the scorching world we see today. It may also provide clues to similar processes on other planets and on young Earth, as Byrne noted:

The thickness of a planet’s lithosphere depends primarily on its temperature, both inside and on the surface. The heat flux from young Earth’s interior was up to three times what it is now, so its lithosphere may have been similar to what we see on Venus today: no thick enough to form plaques that subduct, but thick enough to have fragmented into blocks that pushed, pulled, and shoved.

The discovery of tectonics on Earth’s closest planetary neighbor provides valuable clues about Earth’s “sister planet”. Not as geologically active as Earth, but more active than Mars or the Moon, placing Venus somewhere in between. Venus is a complex and mysterious world, but we are gradually learning its secrets.

Bottom Line: Scientists at North Carolina State University have found evidence of ice floe tectonics on Venus, suggesting the planet may still be geologically active.

Source: A globally fragmented and mobile lithosphere on Venus

Via NC State University

Via conversation

Read more: Cool! This is what Venus would look like as a terraformed aquatic world

About Lucille Thompson

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