Late Accretion onto Terrestrial Planets

The Earth and the Earth-like (terrestrial) planets in the inner Solar System were formed by collisions between protoplanets. In what is thought to be the last of these gigantic collision events, the Earth collided with a Mars-sized body (also known as Theia). 

It is believed that, upon impact, a large quantity of rock fragments, molten material and, in some cases, vapourised matter was hurled into Earth’s orbit, where it coalesced (accreted) to form the Moon. The aim of this research project is to understand how, following this colossal collision, the Earth evolved from a molten body—presumably covered by an ocean of magma several thousand kilometres thick and possessing a metallic core—into a habitable planet with liquid water on its surface, an atmosphere and a biosphere. 

The focus is on the period immediately following the Moon’s formation 4.5 billion years ago up to around 3.8 billion years ago, when the last major lunar maria were formed by large impacts from cosmic bodies. Physical, chemical and mineralogical processes (cooling, crystallisation and material separation) within the Earth’s interior, but above all the intense bombardment by cosmic bodies (impacts), which supplied additional material but also contributed to the heating of the interior, make this period—the so-called ‘Late Accretion Phase’—particularly important for the history of the Earth’s development. As almost no rock relics from this period have survived on Earth, the Moon takes on particular significance. It effectively serves as an archive for the multitude of impact events that must also have taken place on Earth during the same period.

Together with various partners, the MfN is contributing its expertise in the field of impact and shock wave physics and meteorite research to the research project. In particular, with the aid of numerical models developed at the MfN (iSALE), it is possible to investigate the formation of large impact basins on the Moon, mixing and transport processes caused by the ongoing bombardment by asteroids, the formation of the Moon, and the creation of a global or partial magma ocean through impact processes and the incorporation of material from the impactor (in particular its metallic core) into the Earth’s interior.
 

Partners

Freie Universität Berlin (FUB)
Technical University of Berlin (TUB)
University of Münster (WWU)