Venus reveals a provocative new mystery

Contributed by
Apr 30, 2017

Venus has a hot secret, and while this may sound more like the love goddess than the planet, what astronomers recently analyzed about its surface could mean a startling parallel with early Earth.

Despite its killer atmosphere swirling with clouds of sulfuric acid and a surface that would incinerate anything alive, Venus is actually synonymous to Earth in terms of size, mass, distance and even (never mind the acid clouds) chemical composition. That’s about the end of what they have in common—or at least it was believed to be until now.

Volcanoes are heating up on Venus, something scientists thought impossible on a planet with a crust that is so much hotter and softer than Earth’s. Its immensely closer proximity to the sun has everything to do with that. It was thought to be impossible for volcanoes to exist on a planet that never cooled enough for plate tectonics to happen. Surface plates on Earth are always shifting over the silicate-rich mantle, which may seem solid but actually behaves as extremely viscous melted rock. This is the phenomenon that is constantly shifting the positions of the continents, and when shifts happen, so do earthquakes and volcanoes.

If the Venusian surface isn’t rigid enough to crack for plate tectonics to occur, then what are those mysterious circular structures that look suspiciously like volcanoes?

Coronae, which appear like crowns fit for a planetary goddess from above and are found nowhere else, were previously observed on the surface of Venus, but there was a mystery lying beneath. They appeared like volcanoes even though they were rising from a surface thought to have been stagnant for billions of years. Now a recent study published in the journal Nature Geoscience has suggested through lab simulations that they are formed by underlying plumes of scorching molten rock ascending through the mantle, with the surrounding rock sinking beneath their rims forming trenches.

Researchers experimented with fluids loaded with silica particles, which they poured into glass tanks. They dried the fluids from above to simulate the gradual cooling and hardening of Venus’ surface while heating them from below for an up-close view on how rock would be pushed around by the planet’s boiling innards. Results suggested mushroom plumes of scorching rock rise from the mantle and settle under areas on the surface as they similarly do on Earth. Surprisingly, the mantle plumes produced in the lab fractured what appeared to be a rigid surface, meaning magma could ooze through the cracks. What was supposed to simulate surface rock subducted (sank) beneath the rims of rock that surrounded the pillars, a phenomenon called plume-induced subduction.

This new insight could be illuminating the processes that raged on a nascent Earth that was still very much a mass of molten rock billions and billions of years ago.

"What we see on Venus today may be very similar to an earlier phase on Earth," said physicist Anne Davaille of the University of Paris-Saclay, lead author of the new research. "Studying these processes on Venus sheds light on the conditions needed for planets to develop plate tectonics, and may shed light on our origins."