Simulations Link Moon-Sized Impactor to Venus' Strange Rotation
New simulations propose that Venus' unusually slow, backward rotation was likely initiated by a high-angle collision with a fast-moving object approximately one-tenth its mass. This impact, believed to have occurred within the first 50 million years of Venus' formation, could have dramatically altered the planet's spin and melted nearly its entire mantle. The findings were presented at the European Geosciences Union General Assembly in Vienna, offering a potential explanation for a long-standing planetary science puzzle.
Planetary scientists have long been puzzled by Venus' extraordinarily slow retrograde rotation on its axis. New simulations suggest that a high-angle collision with a fast-moving, moon-sized object may have triggered this distinctive 248-day rotation.
The research, presented at the recent European Geosciences Union General Assembly in Vienna, indicates that this impact likely happened within the first 50 million years of Venus' formation. The models propose that an impactor roughly one-tenth of Venus' mass, striking the planet at a high angle, could significantly slow down an early, rapidly rotating Venus.
Cedric Gillmann, the paper's lead author and a planetary scientist at ETH Zurich, stated that the simulations can reduce a rapidly rotating early Venus to rotation rates consistent with long-term evolution towards a slow rotation. In some instances, a large, energetic tangential impact could even lead to an early retrograde, albeit faster, rotation.
The simulations also reveal that such giant impacts would produce surface magma oceans. The depth of these magma oceans could range from a shallow 100km melt layer to a fully molten mantle, depending on the impact properties. If the surface efficiently radiates heat into space, these magma oceans would cool quickly.
If the proposed scenario is accurate, the impactor responsible for Venus' rotation also melted about 99 percent of its mantle, the internal structure between the core and crust. Gillmann noted that this impact heat would dissipate efficiently, making it difficult to distinguish the planet's evolution from a non-impact scenario after a few hundred million years. The potential role of this impact in Venus' lack of plate tectonics remains a topic of ongoing debate, though the absence of a large-scale carbon recycling mechanism is known to have contributed to its current runaway greenhouse effect.
(Source: Slashdot)
