Giant Impacts on Venus 

Abstract

Venus is similar to Earth in terms of mass and size and is sometimes also referred to as “Earth’s twin”. Nevertheless, there are some significant differences between the two planets such as their atmospheric mass and composition, geophysical activity, rotation, and magnetic field.  The origins for the differences between the two planets are still unknown. Since giant impacts are expected to be common in the early evolution of the solar system, it is likely that Venus also experienced an impact. Giant impacts on Venus have likely played an important role in shaping its geological and atmospheric evolution, impacting factors such as volcanic activity and surface composition. Investigating such impact events could provide an improved understanding of Venus' present-day characteristics. Furthermore, contrasting the consequences of impacts on Venus and on other terrestrial planets like Earth and Mars provides a comparative framework for analyzing their histories, and valuable insights into the underlying factors that influence the evolution and the internal structure of terrestrial planets.In this research we explore a range of possible impacts on Venus and investigate their effects on Venus evolution.  We present results from ultra-high resolution simulations of giant impacts on Venus using  Smoothed Particle Hydrodynamics (SPH).  Venus’ interior pre-impact is assumed to consist of an iron core (30% of Venus’ mass) and  a forsterite mantle (70% of Venus’ mass), where the planetary mass is set to be Venus’ current mass.  We also consider models where Venus has a primordial atmosphere with a mass of 1% of Venus’ mass. We allow for different atmospheric compositions including: hydrogen, hydrogen-helium, water, CO and CO2.  For the impactors we assume differentiated bodies with masses ranging from 10-4 – 0.1  Earth masses. Impact velocities vary between 10 and 30 km/s, which translates to roughly 1 - 3 times Venus’ escape velocity. We also consider different impact geometries (head-on and oblique) and a range of pre-impact rotation rates for Venus. We show how different impact conditions lead to different post-impact composition, thermal profiles and rotation periods. We also quantify atmospheric losses caused by the impacts in various scenarios, most relevant for highly energetic collisions.   Finally, we use the impact results to infer the post-impact thermal profile of Venus and explore how it affects Venus’ long-term thermal evolution and current-state internal structure. We then identify the impact scenarios that are most consistent with Venus’ observed properties.  Our research clearly demonstrates that an exploration of giant impacts on Venus can provide valuable insights into the fundamental processes shaping terrestrial planets. This understanding not only enhances our comprehension of planetary evolution within our solar system but also extends to terrestrial exoplanets.