Billions of years ago, Venus may have had a key feature similar to Earth’s | ET REALITY


Venus today is not like Earth. Temperatures hover around 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 suggests that Venus in its youth may have possessed a key Earth-like trait: plate tectonics, the continuous reshaping of pieces of the planet’s outer crust.

“One of the conclusions of this study is that it is very likely that both planets had tectonic plates functioning at approximately the same time period,” said Matthew B. Weller, a planetary scientist at the Lunar and Planetary Institute in Houston, who led the research.

If true, that suggests Venus could have been much more like Earth in other ways. Geochemical reactions of plate tectonics could have buried much of the carbon dioxide that makes Venus so hellish today.

This fuels the idea that a few billion years ago, Venus may have been a place where life could have thrived.

“That’s a very likely scenario,” Dr. Weller said. “This suggests that Venus would certainly have been colder and then there would have been more liquid water.”

Dr. Weller and his colleagues at Brown University and Purdue University did not detect any fractures similar to the San Andreas Fault or other telltale visual signs of plate tectonics. Rather, they looked at the air, particularly nitrogen.

When rocky planets like Earth and Venus form, nitrogen becomes locked in minerals. But in volcanic eruptions, minerals melt and chemical bonds break, and then nitrogen can escape into the atmosphere, where it tends to stay.

“So nitrogen really becomes this kind of diagnostic tool” for understanding a planet’s tectonic history, Dr. Weller said.

The scientists then ran computer simulations exploring two types of tectonic models. One was what is called the stagnant lid, which describes worlds like Mars and Earth’s Moon where the outer crust consists of a solid, immobile layer. Most gases remain trapped beneath the outer shell of the crust.

The second model was plate tectonics. On Earth, about 80 percent of volcanism occurs along mid-ocean ridges, where two tectonic plates are moving apart and magma surfaces. That releases much more gas into the atmosphere.

If Venus had always had a stagnant capped crust, as it appears to have now, simulations indicated there would be less nitrogen than is observed today: 3.5 percent of the atmosphere.

The explanation that worked was a combination of the two models: an early phase of plate tectonics that released abundant carbon dioxide and nitrogen, followed by the crust encased in a stagnant lid.

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

Cédric Gillmann, 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, they depend a lot on what is included and what is left out.” ”. .”

Joseph O’Rourke, a professor of Earth and space exploration at Arizona State University, said perhaps Venus’ geologic history didn’t fit neatly with either Earth-like plate tectonics or a plate tectonics like Earth’s. from Mars.

“Maybe Venus is something intermediate between Earth and Mars,” he said.

A proposed alternative explanation is called the softcover plutonic model: magma penetrates the outer crust, or lithosphere, without dividing it into tectonic plates. That could explain the circular features called coronas on the surface of Venus, pushed up by plumes of hot material rising from the mantle.

“The lithosphere is stickier and has localized breaks,” Dr O’Rourke said.

Dr. Weller said that in the softcover plutonic model, most of the magma never reaches the surface and therefore most likely will not release jets of nitrogen.

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

NASA’s Davinci spacecraft, tentatively scheduled to launch in 2029, will use a parachute-launched probe to make precise measurements of gases in the atmosphere, providing clues about modern-day volcanism.

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

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

The European Space Agency also plans to launch a robotic mission, EnVision, to help scientists understand why conditions on Earth and Venus diverged so much.

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

“That was the original idea of ​​the work,” Dr. Weller said, “and it quickly migrated to being able to explain something about Venus.”

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