Using Impacts to Initiate a Mobile-Lid Regime on Venus

Abstract:

Venus shows a wide array of differences to Earth, though theoretically they are very similar. The surface of Venus shows evidence of a total resurfacing 500-700 million years ago. The current state of Venusian geologic activity is debated; there is evidence for modern-day deformation of the Venusian lithosphere, as well as surface features with no analogous formations here on Earth. Venus is hypothesized to be under stagnant-lid conditions, similar to hypothesized conditions of Hadean Earth. Recent work suggests that in order to have a mobile-lid regime, as Earth does today, a component of degree-1 density structure is required. It has also been hypothesized that a large planetary impact was the trigger for mobile-lid conditions on Earth. Using the geodynamics code ASPECT, cases were run varying the size of the impacting body onto a Venus-like planet. The impacts were translated into perturbations of the temperature field as a function of pressure and run forward in time. Results showed three major ending states: small impacts with no effect globally, moderate impacts with localized effects that grew throughout geologic time, and large impacts causing immediate global upheaval. These findings agree with other hypotheses, however even the smallest case involves an impacting body with a radius far larger than what would be expected within the last billion years of the Solar System. Here we build on these results, further testing the effects of impact-triggered mobile-lid conditions on Venus.