What the Hell, Venus

Venus and Earth have similar masses, densities and distances from the Sun, yet they are radically different rocky worlds. The origin of these differences is debated. It is unclear, for instance, to what extent Venus’s lack of plate tectonics and its dense atmosphere may be the result of the planet’s formation or due to billions of years of evolution.

The Earth’s shifting plates continuously reshape its surface as chunks of the crust collide to form mountain ranges, and in places promote volcanism. Venus has more volcanos than any other planet in the solar system but has only one continuous plate for its surface. More than 80,000 volcanos — 60 times more than Earth — have played a major role in renewing Venus’s surface through floods of lava, which may continue to this day.

Earth and Venus formed in the same neighborhood of the solar system as solid materials collided with each other and gradually combined to form the two rocky planets. However, the slight differences in the planets’ distances from the Sun changed their impact histories, particularly the number and outcome of these events. These differences arise because Venus is closer to the Sun and moves faster around it, energizing impact conditions. In addition, the tail of collisional growth is typically dominated by impactors originating from beyond Earth’s orbit that require higher orbital eccentricities to collide with Venus rather than Earth, resulting in more powerful impacts (Figure 1).

These results gave us an idea. What if these differences in the early impact history of Venus could explain how Earth’s sister planet has maintained a youthful surface despite lacking plate tectonics?

If impacts on Venus had significantly higher velocity than on Earth, a few large impacts could have had drastically different outcomes, with important implications for the subsequent geophysical evolution. We combined large-scale collision modeling and geodynamic processes to assess the consequences of those collisions for the long-term evolution of Venus.

Figure 1. An artistic rendering of a large collision on Venus. (click here to enlarge in a new page) (SwRI/Marchi).

We found that Venus's higher-speed, higher-energy impacts would have created a superheated core that promoted extended volcanism and resurfaced the planet. Our models show that long-lived volcanism driven by early, energetic collisions on Venus offers a novel and compelling explanation for its young surface age.

This research was published in the July 20th 2023 issue of Nature Astronomy (here).