Why is Venus so much more youthful than Earth? Age-blasting impacts offer clue

Venus, on the other hand, boasts more volcanoes than any other planet in our solar system but possesses only one continuous plate for its surface.

A staggering 80,000 volcanoes, 60 times more than Earth, have played a pivotal role in renewing Venus' surface through massive lava floods, possibly even to this day. 

Previous simulations had struggled to explain such extensive volcanism on Venus, but the latest models now provide a compelling explanation.

"Our latest models show that long-lived volcanism driven by early, energetic collisions on Venus offers a compelling explanation for its young surface age," said Professor Jun Korenaga, a co-author from Yale University, in a press release. 

Significantly, if impacts on Venus had been much faster and stronger than those on Earth, just a few large impacts could have caused very different outcomes. This would have had a significant effect on the way the planet evolved geophysically.

Dr. Raluca Rufu, the study's co-author from SwRI, clarified these higher impact velocities led to extensive melting, with up to 82 percent of Venus' mantle becoming molten. Subsequently, a mixed mantle of molten materials and a superheated core formed. 

"Venus' internal conditions are not well known, and before considering the role of energetic impacts, geodynamical models required special conditions to achieve the massive volcanism we see at Venus," Korenaga added. 

Hence the team combined expertise in both collision modeling and geodynamic processes to conclude that energetic impacts could account for the massive volcanism observed on Venus.

"Interest in Venus is high right now," said lead author Dr. Simone Marchi. 

"These findings will have synergy with the upcoming missions, and the mission data could help confirm the findings."

As we unravel the mysteries of Venus and its unique geological evolution, these new findings offer a pathway to understanding the planet's youthful appearance and the intriguing natural engineering that sets it apart from Earth.

The complete study was published in Nature Astronomy and can be accessed here.

Study abstract:

The geodynamics of Earth and Venus operate in strikingly distinct ways, in spite of their similar size and bulk density, resulting in Venus's absence of plate tectonics and young surface age (0.2–1 billion years). Venus's geophysical models have sought to explain these observations by invoking either stagnant lid tectonics and protracted volcanic resurfacing, or by a late episode of catastrophic mantle overturn. These scenarios, however, are sensitive to poorly understood internal initial conditions and rheological properties, and their ability to explain Venus's young surface age remains unclear. Here we show that long-lived volcanism, driven by early, energetic collisions on Venus, offers an explanation of its young surface age with stagnant lid tectonics. This volcanic activity is fuelled by a superheated core, resulting in vigorous internal melting regardless of initial conditions. Furthermore, we find that energetic impacts stir Venus's core, suggesting that its low magnetic field is not likely to be caused by a compositionally stratified core, as previously proposed.