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Updated: Jan 10, 2026
06:04
Simulation of the Planetary Interior Differentiation Processes in the Laboratory
Published on: November 15, 2013
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The Moon-forming impactor Theia originated from the inner Solar System.
Timo Hopp1,2, Nicolas Dauphas1,3, Maud Boyet4
1Department of the Geophysical Sciences, The University of Chicago, Chicago, IL, USA.
Science (New York, N.Y.)
|November 20, 2025
Summary
The Moon likely formed from a giant impact with Theia, a protoplanet originating in the inner Solar System. Iron isotope analysis reveals Earth and Moon share similar compositions, suggesting a shared origin closer to the Sun.
Area of Science:
- Planetary Science
- Geochemistry
- Cosmochemistry
Background:
- The Moon's formation is attributed to a giant impact between proto-Earth and a Mars-sized body named Theia.
- Theia's formation location, whether in the inner or outer Solar System, remains uncertain.
Purpose of the Study:
- To determine the origin of Theia and proto-Earth by analyzing iron isotope compositions.
- To constrain the formation location of Theia using isotopic data and mass balance calculations.
Main Methods:
- Measurement of iron isotopes in lunar samples, terrestrial rocks, and meteorites.
- Comparison of isotopic compositions to represent potential reservoirs for Theia and proto-Earth.
- Mass balance calculations integrating iron isotope data with other elemental abundances.
Main Results:
- Earth and Moon exhibit indistinguishable mass-independent iron isotopic compositions.
- These compositions align with one extreme end of the meteorite isotopic range.
- Mass balance calculations indicate Theia and most of Earth's material originated from the inner Solar System.
Conclusions:
- Theia likely formed in the inner Solar System, potentially closer to the Sun than Earth.
- The isotopic similarity between Earth and Moon supports a shared origin from inner Solar System materials.
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