Once habitable Venus was likely killed by millennia of volcanic eruptions, NASA says

Venus is among the biggest mysteries in the solar system because it’s “a hellish world” that NASA believes was once habitable, including flowing water and a shallow ocean.

So what happened?

The simple answer is volcanoes, NASA says.

Eruptions began on Venus and didn’t stop, even as decades became centuries and centuries became millennia, according to the recently released study “Large-scale Volcanism and the Heat Death of Terrestrial Worlds.”

“Volcanic activity lasting hundreds to thousands of centuries and erupting massive amounts of material may have helped transform Venus from a temperate and wet world to the acidic hothouse it is today,” NASA said in a news release.

To understand the startling change, scientists used Earth’s history of “major mass extinction events” as a measure, the report says.

During such periods, “massive volcanic outpourings” exceeding 100,000 cubic miles flowed across the surface. “At the upper end, this could be enough molten rock to bury the entire state of Texas half a mile deep,” NASA says.

It was these ancient volcanic outpourings — and not rogue asteroids — that killed much of ancient life on Earth, scientists say.

“Contrary to widely held belief, volcanism, rather than impactors (asteroids), has had the greatest influence on and bears most of the responsibility for large-scale mass extinction events throughout Earth’s history,” the report says.

“The occurrence of several such eruptions (on Venus) in a short span of geologic time (within a million years) could have led to a runaway greenhouse effect which kicked off the planet’s transition from wet and temperate to hot and dry.”

The average temperature on Venus is 864 degrees, one day is the equivalent to 117 Earth days, and it has a “crushing carbon dioxide atmosphere 90 times as thick as Earth’s,” NASA says. Even more telling: “large fields of solidified volcanic rock cover 80% of the planet.”

Such fields are known as “large igneous provinces” and they can be planet killers, NASA says.

“Life on Earth has endured at least five major mass extinction events since the origin of multicellular life about 540 million years ago, each of which wiped out more than 50% of animal life across the planet,” NASA says.

“According to this study and others before it, the majority of these extinction events were caused or exacerbated by the kinds of eruptions that produce large igneous provinces. In Earth’s case, the climate disruptions from these events were not sufficient to cause a runaway greenhouse effect as they were on Venus, for reasons ... scientists are still working to determine.”

The study suggests Earth may have “narrowly” avoided the climatic effects “responsible for the heat death of our sister world Venus.”

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