The surface of Venus moves like ice floating on an ocean

The Research Brief is a short take about interesting academic work.

The big idea

Much of the brittle, upper crust of Venus is broken into fragments that jostle and move – and the slow churning of Venus’ mantle beneath the surface might be responsible. My colleagues and I arrived at this finding using decades-old radar data to explore how the surface of Venus interacts with the interior of the planet. We describe it in a new study published in the Proceedings of the National Academy of Sciences on June 21, 2021.

Planetary scientists like me have long known that Venus has a plethora of tectonic landforms. Some of these formations are long, thin belts where the crust has been pushed together to form ridges or pulled apart to form troughs and grooves. In many of these belts there’s evidence that pieces of the crust have moved side to side, too.

Our new study shows, for the first time, that these bands of ridges and troughs often mark the boundaries of flat, low-lying areas that themselves show relatively little deformation and are individual blocks of Venus’ crust that have shifted, rotated and slid past each other over time – and may have done so in the recent past. It’s a little like Earth’s plate tectonics but on a smaller scale and more closely resembles pack ice that floats atop the ocean.

Researchers have hypothesized that – just like Earth’s mantle – the mantle of Venus swirls with currents as it’s heated from below. My colleagues and I modeled the sluggish but powerful movement of Venus’ mantle and showed that it is sufficiently forceful to fragment the upper crust everywhere we’ve found these lowland blocks.

Why it matters

A major question about Venus is whether the planet has active volcanoes and tectonic faulting today. It’s essentially the same size, composition and age as Earth – so why wouldn’t it be geologically alive?

But no mission to Venus has yet conclusively shown the planet to be active. There’s tantalizing but ultimately inconclusive evidence that volcanic eruptions have taken place there in the geologically recent past – and are perhaps even ongoing. The case for tectonic activity – the creaking, breaking and folding of the planet’s crust – is on even less solid ground.

Showing that Venus’ geological engine is still running would have huge implications for understanding the composition of the planet’s mantle, where and how volcanism might be taking place today and how the very crust itself is formed, destroyed and replaced. Because our study suggests that some of this jostling of the crust is geologically recent, we may have taken a big step forward in understanding if Venus really is active today.

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