Unraveling Venus’s Rotation Mystery
A new study presented at the European Geosciences Union General Assembly in Vienna offers a fresh explanation for Venus’s unusual rotation. According to the research, the planet’s 248-day retrograde spin could have been caused by a collision with a Moon-sized object. This impact likely occurred within the first 50 million years of Venus’s formation.
The impacting body is estimated to have been about ten times less massive than Venus itself. The collision melted roughly 99 percent of the planet’s mantle, creating a molten layer approximately 100 kilometers thick. Today, Venus has a surface temperature of 467 °C and an atmospheric pressure 92 times greater than Earth’s.
The Critical Role of Impact Angle
Researchers emphasized the importance of the collision’s angle. According to lead researcher Cedric Gillmann,
“We wanted to explore whether an impact could alter a planet’s rotation. But it would have needed to be a high-angle strike to significantly change the planet’s initial spin.”The team is working to reconcile Venus’s original rotation conditions with its current characteristics.
Gillmann described the experiment as “throwing a large rock into another very large rock” to understand how planetary deformation affects rotation and internal properties like temperature. The scientists noted that depending on impact parameters, a fast-spinning early Venus could have been slowed to speeds consistent with its long-term evolution into a slow rotator.
Furthermore, the study suggests that a high-energy tangential impact could flip an early planet into retrograde rotation. This finding may also explain why, over the last billion years, about 20 billion cells have been transferred from Earth to Venus, with roughly 100 Earth cells dispersing annually in Venus’s atmosphere.
These results, presented at the 2026 Lunar and Planetary Science Conference (LPSC), could significantly reshape our understanding of Venus’s geological history and planetary evolution. Source: Phys.org.
Understanding Venus’s rotation has broader implications for how planets form and evolve in our solar system. Uncovering new mechanisms that can alter planetary spins opens fresh avenues in planetary geology and astronomy. It may also prove vital for studying exoplanets and their potential characteristics, aiding the search for life beyond Earth.