Early impacts on venus led to long-lived volcanism

The surface of Venus, Earth’s sister planet, has remained surprisingly youthful over the ages, despite lacking Earth’s dynamic plate tectonics. A team led by the Southwest Research Institute delved into this mystery by studying the early impact history of Venus and comparing it to Earth’s. Their findings, published in Nature Astronomy, propose that Venus experienced high-speed, high-energy collisions during its early history, leading to a superheated core that fueled prolonged and intense volcanism. This volcanic activity, in turn, has continuously resurfaced the planet, resulting in a landscape with over 80,000 volcanoes, which is 60 times more than Earth.

The contrast between Earth and Venus lies in their geological processes. On Earth, the movement of tectonic plates shapes the surface, forming mountains and facilitating volcanism. In contrast, Venus has a single continuous plate on its surface, yet it exhibits an extraordinary number of volcanoes that have played a major role in renewing its terrain with lava floods, possibly still ongoing today. Previous attempts to explain this level of volcanism on Venus through simulations have been challenging.

The new models proposed by the research team indicate that the key to understanding Venus’s young surface lies in the early energetic collisions it experienced. These powerful impacts led to a superheated core, triggering intense internal melting and sustaining long-lasting volcanic activity. Professor Jun Korenaga from Yale University, a co-author of the study, emphasized that this massive volcanic activity is driven by the superheated core of Venus, which continues to shape and resurface the planet’s terrain.

This high resolution (1 million particles) computer simulation illustrates an 1,800-mile-diameter (3,000-kilometer) projectile striking Venus head-on at 18 miles per second (30 km/s). On the left, the colors indicate different materials — brown for Venus’ core; white for the projectile’s core; and green for the silicate mantle of both objects. The colors on right side indicate the temperature of the materials. Credit: Southwest Research Institute

Both Earth and Venus originated in the same region of the solar system, where solid materials collided and gradually coalesced into rocky planets. However, subtle differences in their distances from the sun led to distinct impact histories for each planet.

Venus’s closer proximity to the sun means it orbits at a faster pace, resulting in more energized impact conditions compared to Earth. Moreover, the types of impactors in the region beyond Earth’s orbit play a significant role. These impactors require higher orbital eccentricities to collide with Venus rather than Earth, leading to more powerful collisions on Venus.

The higher impact velocities on Venus have profound effects. They cause a substantial melting of silicate material, melting up to 82% of Venus’s mantle. This process creates a mixed mantle with molten materials distributed globally, and it also contributes to the formation of a superheated core.

Dr. Raluca Rufu, a Sagan Fellow and co-author from SwRI, highlights that these intense impact events have left Venus with a molten mantle and a superheated core, setting it apart from Earth and shaping its geological processes.

A Southwest Research Institute-led team has modeled the early impact history of Venus to explain how Earth’s sister planet has maintained a youthful surface despite lacking plate tectonics. The new model suggests that the planets’ distances from the Sun resulted in higher-energy, higher-velocity impacts to Venus. These powerful collisions created a superheated core that promoted extended, extensive volcanism and resurfaced the planet. Credit: Southwest Research Institute

The impact velocities on Venus, being significantly higher than on Earth, could have led to drastically different outcomes with profound implications for its geological evolution. To understand the consequences of such collisions on Venus, a multidisciplinary team combined expertise in large-scale collision modeling and geodynamic processes.

One of the significant challenges was the limited knowledge about Venus’s internal conditions. Geodynamical models, to explain the massive volcanism observed on Venus, required special conditions that didn’t fully align with reality. However, when the team introduced energetic impact scenarios into the model, it remarkably and naturally explained the extensive and prolonged volcanism without needing major parameter adjustments.

The timing of these discoveries aligns perfectly with NASA’s commitment to two new Venus missions, VERITAS and DAVINCI, and the European Space Agency’s planned mission called EnVision, all slated for the future. The surge of interest in Venus makes these findings particularly relevant, as the upcoming missions may provide valuable data to validate and support the newly proposed explanations about Venus’s geological history. The combination of theoretical modeling and upcoming mission data could lead to a better understanding of our neighboring planet, Venus, and its intriguing geological past.

Source: Southwest Research Institute

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