Impact hypothesis revisited
Venus rotates unusually slowly and in the opposite direction to most planets. Recent computational work indicates that a collision with a body roughly the size of Earth's Moon, occurring around 4.5 billion years ago, could be responsible for this characteristic.
Impact parameters
Models show that a steep‑angle, high‑speed impact can dramatically alter a planet's angular momentum. The transfer of momentum would both reverse the spin direction and reduce its rate, matching current observations.
Research methodology
Scientists employed numerical hydrodynamic simulations, testing a range of projectile masses, velocities, and impact angles. The goal was to identify the most plausible set of conditions that would generate the present retrograde rotation.
Implications for planetary evolution
A catastrophic event of this magnitude would have affected not only Venus' spin but also its geological history. The findings reinforce the idea that massive collisions shaped the early inner solar system.
Future work
Additional observations, including radar and infrared mapping, aim to refine the models and search for surface signatures of the hypothesized impact.