A thermally conductive Martian core and implications for its dynamo cessation

Area of Science:

• Planetary Science
• Geophysics
• Materials Science

Background:

• Mars once possessed a global magnetic field generated by a dynamo process.
• The cessation of this dynamo significantly impacted Mars' evolution.
• Core thermal conductivity is a key factor in dynamo processes.

Purpose of the Study:

• Directly measure the thermal conductivity of iron-sulfur alloys under Martian core conditions.
• Investigate the influence of sulfur content on thermal conductivity.
• Provide data to refine models of Mars' core and its dynamo history.

Main Methods:

• Direct measurement of thermal conductivity of solid iron-sulfur alloys.
• Experiments conducted at pressures relevant to the Martian core.
• Temperatures were controlled up to 1023 Kelvin.

Main Results:

• Measured thermal conductivities for a Martian core composition (16 wt% sulfur) range from 19 to 32 W m⁻¹ K⁻¹.
• These values are significantly higher than those inferred from previous electrical resistivity studies.
• A 4- to 6-fold discontinuity in thermal conductivity across the core-mantle boundary was modeled.

Conclusions:

• High thermal conductivity in the Martian core promotes efficient cooling.
• Efficient cooling leads to thermal stratification, diminishing convection.
• These factors likely contributed substantially to the cessation of the Martian dynamo.