Often referred to as Earth’s evil twin, Venus shares similar size, mass, and composition with our planet but has evolved into one of the most enigmatic bodies in the solar system. Known for its extreme conditions, Venus’s surface temperatures can melt lead, its atmosphere brims with carbon dioxide, and sulfuric acid rains down from its skies. Uniquely, Venus spins backward among the planets, with a rotation period exceeding its year, and it has no moons—a rarity considering its size.
Unlike Earth and Mars, which bear the scars of numerous impact craters, Venus appears to have undergone a significant geological reset, erasing most of its impact history likely due to extensive volcanic activity over millions of years. Yet, new research from the University of Zurich, led by Mirco Bussmann, proposes a dramatic theory: that Venus may have once been struck by an object comparable to Mars.
The Bold New Study
In their groundbreaking simulation, Bussmann and his team visualized a colossal collision, hypothesizing what would transpire if Venus encountered a Mars-sized body. Utilizing Smooth Particle Hydrodynamics (SPH)—a sophisticated computational model—researchers treated the planets as a swarm of responsive particles to observe their behavior during collisions.
In this simulated environment, Venus is portrayed not merely as a solid object, but as comprising a core of iron that constitutes about 30% of its mass, surrounded by a silicate mantle that accounts for the remaining 70%. The researchers tested a range of impactor sizes, from 0.01 to 0.1 times the mass of Earth, with impact velocities between 10 and 15 km/s. By adjusting the initial rotation rates and thermal conditions of Venus, they explored multiple collision scenarios.
Study Conclusions
The findings of the University of Zurich team indicate that a singular, large impact could elucidate two major mysteries surrounding Venus: its slow rotation and lack of a moon. The simulations revealed that various collision dynamics could account for Venus’s current spin, including both direct and glancing impacts. Notably, these interactions typically resulted in minimal debris formation, implying that any material generated would re-enter Venus’s atmosphere rather than contributing to moon formation.
This insight suggests that the absence of a moon might be tied to substantial impacts from a giant extraterrestrial body. Furthermore, if a Mars-sized celestial object did collide with Venus during its formative years, it could have drastically altered the planet’s thermal and geological evolution, introducing immense heat to its interior, disrupting its mantle, and halting plate tectonics—setting the stage for widespread volcanic activity. This intense thermal disruption might explain why Venus exhibits such a young geological surface.
