Earth and Mars were formed from materials missing from the solar system

Artist’s impression of the developing solar system, with the young sun at its center and the (proto-)planets accreting dust and debris from the disc. Credit: NASA

By examining the range of isotopic variations in terrestrial and meteoritic samples, a scientist and collaborators at Lawrence Livermore National Laboratory (LLNL) discovered that the Earth and " data-gt-translate-attributes="[{" attribute="">March formed by collisions of planetary embryos from the inner solar system.

The rocky planets may have formed by two fundamentally different processes, but it is unclear which built the terrestrial planets of our solar system. The planets were formed either by collisions between planetary embryos of the inner solar system, or by the accretion of millimeter “pebbles” drifting towards the sun of the outer solar system.

In the new research, the team showed that the isotopic compositions of Earth and Mars result primarily from the accretion of planetary bodies from the inner Solar System, including materials from the innermost disk not sampled by meteorites, with only a few percentages of a planet’s mass from outer solar system bodies. The research appears in the December 22 issue of Scientists progress.

“Our data refute a pebble accretion origin of terrestrial planets, but are consistent with collisional growth of inner Solar System embryos,” said LLNL scientist and co-author Jan Render, who carried out part measurements while working as a post-doctoral fellow in his previous position. to University of Munster. “This low fraction of outer solar system material on Earth and Mars suggests the presence of a persistent dust and drift barrier in the disc and highlights the specific pathway of formation of rocky planets in the solar system.”

Determining which of the two processes governed the formation of the terrestrial planets of our solar system is crucial for understanding the architecture and dynamic evolution of the solar system, and for placing the formation of planets in the solar system in the context of the general processes of formation of planets, such as those observed in exoplanetary systems.

The amount of material from the outer solar system accreted by terrestrial planets can be determined using nucleosynthetic isotopic anomalies. These arise from the heterogeneous distribution of presolar material within the solar protoplanetary disk and provide a record of the legacy of a planet’s building materials. These isotopic anomalies help distinguish between non-carbonaceous (NC) and carbonaceous (CC) meteorites, which are generally assumed to represent planetary bodies that accreted into the inner and outer solar system, respectively.

The team used the recent observation of correlated isotopic variations among NC meteorites to show that Earth and Mars were incorporating materials not sampled among meteorites, determined the provenance and isotopic composition of this lost planetary building material, and used this information to assess the amount of accreted CC material. by Earth and Mars.

For more on this research, see Earth and Mars were formed from collisions of large bodies made of material from the inner solar system.

Reference: “Terrestrial planet formation from lost inner solar system material” by Christoph Burkhardt, Fridolin Spitzer, Alessandro Morbidelli, Gerrit Budde, Jan H. Render, Thomas S. Kruijer and Thorsten Kleine, December 22, 2021, Scientists progress.
DOI: 10.1126/sciadv.abj7601

Other contributors include researchers from the University of Münster, the University of Nice Sophia-Antipolis, the California Institute of Technology and the Museum für Naturkunde and the Freie Universitat Berlin. The work is funded by the German Research Foundation.

Arline J. Mercier