Constraining Earth's core composition from inner core nucleation

Area of Science:

• Geophysics
• Earth Science
• Planetary Science

Background:

• Earth's core composition is crucial for understanding deep Earth structure, thermal evolution, and magnetic field generation.
• Current models face challenges in reconciling cosmochemical, formation, and seismological data with core composition.
• The role of supercooling in inner core formation has been a debated topic, with some binary core compositions being incompatible with nucleation.

Purpose of the Study:

• To investigate the compatibility of specific iron-carbon (Fe-C) core compositions with inner core nucleation.
• To determine if Fe-C alloys can nucleate under realistic geophysical conditions, addressing supercooling requirements.
• To refine constraints on Earth's core composition by evaluating nucleation behavior.

Main Methods:

• Utilized molecular dynamics simulations to model the nucleation process of the inner core.
• Simulated an iron-carbon (Fe1-xC x=0.1-0.15) composition under relevant pressure and temperature conditions.
• Compared simulation results with existing geophysical constraints on core formation and properties.

Main Results:

• Demonstrated that an Fe-C composition (Fe1-xC x=0.1-0.15) is compatible with inner core nucleation.
• Showed that this specific composition can nucleate without requiring extreme supercooling, aligning with geophysical observations.
• Identified inner core nucleation as a significant factor for discriminating between potential core compositions.

Conclusions:

• Inner core nucleation provides a strong constraint on the possible chemical makeup of Earth's core.
• Iron-carbon alloys are plausible candidates for Earth's core composition, consistent with nucleation dynamics.
• This study advances our understanding of core formation and composition, aiding in the resolution of long-standing geophysical puzzles.