Geochemistry: Silicon in the Earth’s core

Silicon may already have been present in the Earth’s core before the Moon formed.The finding could help explain the isotopic differences in silicon content that exist between various celestial bodies.
The iron isotopes found in basaltic rocks from the Earth and Moon have a relatively heavy atomic mass compared with those from Mars, Vesta and primitive meteorites. But the origin of this has been unclear because other elements do not seem to show the effect. Alex N. Halliday and colleagues now show that the silicon isotopic compositions of basaltic rocks from the Earth and Moon are also distinctly heavy.
That the Earth and Moon share similar isotopic compositions of bulk silicate is consistent with the idea that different isotopes of various elements were mixed up and then reached equilibrium when the young Earth collided with a Mars-sized body to form the Moon. And if so, the authors conclude that silicon was already a light element in the Earth’s core before the Moon formed.

CONTACT
Alex N. Halliday (Oxford University, UK)
Tel: +44 1865 272 969; E-mail: alexh@earth.ox.ac.uk

Tim Elliott (University of Bristol, UK) N&V author
Tel: +44 117 954 5426; E-mail: Tim.Elliott@bristol.ac.uk