Powering Earth's dynamo with magnesium precipitation from the core

Area of Science:

• Geophysics
• Planetary Science
• Earth Science

Background:

• Earth's magnetic field originates from convection in the liquid outer core.
• Palaeomagnetic data indicate the geodynamo has operated for at least 3.4 billion years.
• Standard models propose compositional convection, thermal convection, or radiogenic heating as power sources.

Purpose of the Study:

• To investigate alternative power sources for Earth's geodynamo.
• To reconcile the geodynamo's long-term operation with new findings on iron's thermal conductivity.
• To explain how the geodynamo could persist even with slow cooling or minimal radiogenic heating.

Main Methods:

• Utilizing first-principles calculations and diamond-anvil cell experiments.
• Analyzing the implications of increased iron thermal conductivity on core dynamics.
• Modeling the role of magnesium-bearing mineral precipitation as a buoyancy-driven power source.

Main Results:

• Higher iron thermal conductivity suggests a young inner core, challenging existing geodynamo models.
• Magnesium precipitation from the core provides a more efficient buoyancy source than inner-core growth.
• This process allows for sustained geodynamo operation throughout Earth's history.

Conclusions:

• Magnesium precipitation offers a viable mechanism to power Earth's geodynamo over geological timescales.
• This finding supports the geodynamo's continuous operation from at least 3.4 billion years ago to the present.
• It resolves discrepancies arising from recent high-pressure experimental data on iron.