Icarus 226, 20–32 (2013)

It has been proposed that a giant impact occurred in the first 500 million years of Mars's history. Numerical modelling of the proposed impact's aftermath suggests that the metallic cores of the impactor and Mars would have merged, producing thermal gradients in the deep martian interior that could have driven a short-lived core dynamo.

Julien Monteux at Université de Nantes, France, and colleagues used numerical models to explore the dynamics and thermal effects of metallic iron from an asteroid sinking through the martian mantle to merge with the core. In the simulations, material from the impactor heats the surrounding mantle as it sinks, altering the thermal structure of the martian interior. The core merging would have occurred within a million years after the impact. Because the added heat is mixed into the core, the heat flux across the core–mantle boundary could have been enhanced. This heat-flow in turn could have driven a dynamo that persisted until the added heat had dissipated, over a period of about 100 million years.

However, depending on how the heat from the impactor was mixed into the core, core merging may have also weakened or even inhibited a pre-existing dynamo.