Impacting Theories of the Early Earth

New simulations are providing insight into the events following the formation of the Moon. It is thought that the Moon was created when a large object collided with the early Earth. This resulted a field of debris around our planet, which eventually coalesced into our moon.

After the Moon was formed, the Earth was impacted by leftover planetesimals that delivered additional mass to our planet. This mass has been estimated to be roughly 0.5% of Earth’s present mass. The estimate is based on elements found in Earth’s mantle, and under the assumption that all of the material delivered by impacts was retained in the mantle.

The new study challenges this idea. Using smoothed-particle hydrodynamics impact simulation, researchers showed that portions of large planetesimals impacting the Earth may have descended to the planet’s core, or possibly escaped from accretion with the Earth entirely. The study could change estimates of our planet’s mass during the late accretion phase, and might also explain some isotopic anomalies found in rocks on Earth.

The study, “Heterogeneous delivery of silicate and metal to the Earth by large planetesimals,” was published in the journal Nature Geoscience. This work was supported by the NASA Astrobiology Program through the Exobiology & Evolutionary Biology Program. Support also came from the Emerging Worlds Program. The NASA Astrobiology Program provides resources for Emerging Worlds and other Research and Analysis programs within the NASA Science Mission Directorate (SMD) that solicit proposals relevant to astrobiology research.