Related Experiment Video
Updated: Jan 10, 2026

Simulation of the Planetary Interior Differentiation Processes in the Laboratory
Published on: November 15, 2013
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.
None:
The Moon formed from a giant impact of a planetary body, called Theia, with proto-Earth. It is unknown whether Theia formed in the inner or outer Solar System. We measured iron isotopes in lunar samples, terrestrial rocks, and meteorites representing the isotopic reservoirs from which Theia and proto-Earth might have formed. Earth and the Moon have indistinguishable mass-independent iron isotopic compositions; both define one end of the range measured in meteorites. Combining our results with those for other elements, we performed mass balance calculations for Theia and proto-Earth. We found that all of Theia and most of Earth's other constituent materials originated from the inner Solar System. Our calculations suggest that Theia might have formed closer to the Sun than Earth did.
Related Concept Videos
Gravity between Spherical Bodies
This assumption can be proved easily by showing that the expression for gravitational potential energy between a hollow sphere of mass (M) and a point mass (m) is the same as it would be for a pair of extended...
Gravitation
Circular Orbits and Critical Velocity for Satellites
Nicolaus Copernicus (1473-1543) first suggested that the Earth and all other planets orbit the Sun in...
Kepler's First Law of Planetary Motion
Polish astronomer Nikolaus Copernicus put forth a theory that stated a heliocentric model for the solar system. According to this heliocentric theory, all the planets, including Earth, orbit the Sun in circular orbits.
On the other hand,...
Conditions on Early Earth
Impact
When particles with different initial velocities collide, they induce deformation by applying equal and opposite impulses. At the point of maximum deformation, the particles move together with...

