Did Venus suffer a giant impact?

Among the planets in the solar system, Venus is the most similar to Earth in terms of mass, radius, bulk density, and semi-major axis. Despite these similarities, Venus exhibits very different surface and atmospheric conditions, including surface pressures over 90 times higher, average temperatures of about 740 K, a dense carbon dioxide atmosphere, and clouds composed of sulfuric acid. Furthermore, Venus rotates slowly in a retrograde direction and has no moon. The origin of these differences remains unknown. One possibility is that Venus and Earth shared similar primordial conditions and later diverged during their evolution; another is that they were different from the start. While Earth likely suffered a giant impact that led to the formation of the Moon, it remains uncertain whether Venus experienced such impacts and whether they influenced its current-state characteristics. Giant impacts are thought to be common in the young solar system and, if occurred on Venus, could have affected its thermal evolution, rotational characteristics and presence or lack of moons. In this study, we explore a range of possible giant impacts on Venus using Smoothed Particle Hydrodynamics (SPH) simulations [1, 2, 3, 4]. Assuming a differentiated Venus and impactor composed of a 30% iron core and a 70% forsterite mantle. We simulate collisions with impactors of 0.01 - 0.1 Earth masses, at velocities of 10 - 15 km/s, across varying impact angles and pre-impact rotation states. We show how different impact conditions affect Venus’ post-impact rotation period, thermal profile, and the formation of a debris disk. We find that a wide range of giant impact scenarios are compatible with Venus’ present-day rotation period and lack of a moon. This implies that it is possible that Venus, like the other terrestrial planets, suffered from a giant impact shortly after its formation which influenced Venus’ subsequent thermal evolution. In a subsequent study (Gillmann et al., in prep.) we follow the thermal evolution of post-impact Venus and investigate which impact conditions are consistent with present-day Venus. References[1] Potter et al. 2017, doi.org/10.1186/s40668-017-0021-1[2] Reinhardt & Stadel 2017,  doi.org/10.1093/mnras/stx322[3] Reinhardt et al. 2020, doi.org/10.1093/mnras/stz3271[4] Meier et al. 2021, doi.org/10.1093/mnras/stab144