Giant impact stratification of the Martian core

Abstract

We investigate the direct thermal effects of giant impacts on the Martian core and its dynamo. Shock wave heating of Mars is calculated in terms of the impact velocity and the final basin size. Although much of the shock wave heat is deposited in the mantle, shock heating from a giant impact produces non‐uniform temperatures in the core, leading to an overturn event and stable thermal stratification in the liquid core. Numerical dynamos with core heating from polar and equatorial impacts show that the overturn and stratification quickly destroys a pre‐existing core dynamo, within ten thousand years. Energy considerations reveal that both the stratification and the time required for removal of the stratification increase with impact size. Our calculations indicate that several tens to over one hundred million years are required for removal of core stratification following a giant impact.