February 25, 2024

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Venus may have had Earth-like tectonic plates billions of years ago

Venus may have had Earth-like tectonic plates billions of years ago

Today’s Venus is not like Earth. Temperatures reach about 860 degrees Fahrenheit day and night, and clouds of sulfuric acid float in its atmosphere.

But a study published Thursday In the journal Nature Astronomy It suggests that Venus in its youth may have had a key Earth-like feature: plate tectonics, the constant reshaping of parts of the planet’s outer crust.

“One of the findings of this study is that it is very likely that both planets had plate tectonics operating at roughly the same time period,” said Matthew P. Wheeler, a planetary scientist at the Lunar and Planetary Institute in Houston who led the research.

If true, this suggests that Venus could have been similar to Earth in other ways. The geochemical interactions of tectonic plates may have buried much of the carbon dioxide that makes Venus so hellish today.

This adds substance to the idea that a few billion years ago, Venus may have been a place where life could have flourished.

“This is a very likely scenario,” Dr. Wheeler said. “It indicates that Venus was definitely cooler and therefore there would be more liquid water.”

Dr. Wheeler and his colleagues at Brown University and Purdue University did not observe any San Andreas Fault-like fractures or other visible signs of plate tectonics. Instead, they looked at air, especially nitrogen.

When rocky planets like Earth and Venus form, nitrogen is trapped in minerals. But in volcanic eruptions, minerals dissolve and chemical bonds break, so nitrogen can escape into the atmosphere, where it tends to linger.

“So nitrogen has really become this kind of diagnostic tool” for understanding the planet’s tectonic history, Dr. Wheeler said.

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The scientists then set up computer simulations to explore two types of tectonic models. One was the so-called stagnant mantle, which describes worlds like Mars and Earth’s moon where the outer crust consists of a solid, immobile crust. Most of the gases remain trapped under the outer crust.

The second model is plate tectonics. On Earth, about 80% of volcanic activity occurs along mid-ocean ridges where tectonic plates spread apart and magma wells rise. This releases more gas into the atmosphere.

If Venus has always had a stagnant mantle, as it appears now, simulations have suggested less nitrogen than we observe today — 3.5% of the atmosphere.

The explanation that worked was a combination of the two models: an early stage of plate tectonics that released copious amounts of carbon dioxide and nitrogen, followed by the crust being locked into a stagnant mantle.

Scientists not involved in the research said the results were suggestive but not conclusive.

Cédric Gellman, a planetary scientist at the Swiss Federal Institute of Technology who was not involved in the research, said the paper was interesting but cautioned that “as with all model-based publications, it relies heavily on what is included and what is omitted.” “.

Venus’s geological history may not have been perfectly compatible with Earth-like plate tectonics or a Mars-like stagnant mantle, said Joseph O’Rourke, a professor of Earth and space exploration at Arizona State University.

“Maybe Venus is its own thing that’s in the middle between Earth and Mars,” he said.

One proposed alternative explanation is called the subsurface model, in which magma intrudes the outer crust, or lithosphere, without breaking up into tectonic plates. This could explain the circular features called coronas on Venus’ surface, which are pushed upward by plumes of hot material rising from the mantle.

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“The lithosphere is more viscous and has localized fracture,” Dr. O’Rourke said.

In the subterranean sponge mantle model, most of the magma never reaches the surface and therefore may not release fluxes of nitrogen, Dr. Wheeler said.

Spacecraft heading to Venus in the coming years are supposed to provide important new data to help solve mysteries. Dr. O’Rourke noted that he had just been born when Magellan, the last NASA mission there, entered orbit in 1990. “I was about 10 days old,” he said. “So I’m excited to see some new Venus missions in my lifetime.”

NASA’s da Vinci spacecraft, tentatively scheduled to launch in 2029, will use a parachute probe to make precise measurements of gases in the atmosphere, providing evidence of current volcanic activity.

Another expected NASA mission, VERITAS, will make detailed measurements of the planet’s gravity and take high-resolution images of the surface.

“This will really help us look for possible plate boundaries,” said Anna Goelcher, a planetary scientist at the California Institute of Technology and NASA’s Jet Propulsion Laboratory.

The European Space Agency is also planning to launch a robotic mission, called EnVision, to help scientists understand why conditions on Earth and Venus are so different.

Dr. Wheeler’s computer models could also help shed light on the geological history of planets orbiting other stars by studying what is detected in the air around them.

“That was the original idea for the work, and it quickly moved on to being able to explain something about Venus,” Dr. Wheeler said.