Diamond anvils probe the origins of Earth’s magnetic field

Abstract

Why is Earth covered by oceans and teeming with life, when Mars remains arid and apparently lifeless? The reasons are many, ranging from atmospheric characteristics to the planet’s distance from the Sun. But one key condition may involve the ability of the Earth’s core to generate a magnetic field. Diamond anvils squeeze samples to extreme pressures while probing them with lasers directed through the diamonds. Geophysicists use the anvils to simulate the extreme pressures of the Earth’s interior. Image courtesy of Sergey Lobanov (Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC). And yet the origins of the Earth’s magnetic field remain a mystery for a variety of reasons. For one, there’s the small matter of accessing that chiefly iron core, which is buried under 1,800 miles of rock. This has left scientists resorting to lasers and diamond anvils in the laboratory to heat and squeeze iron to recreate the kind of temperatures and pressures found in the deep Earth. Thus far, these experiments have offered conflicting results, raising more questions than answers (1, 2). Earth’s magnetic field is generated by its dynamo: the electrically conducting liquid metals in the planet’s outer core that churn or convect because of heat, like boiling water roiling in a pot. The strength of this convection depends on how much heat flows from the outer core to Earth’s mantle, which in turn depends on the thermal conductivity of iron and its alloys. The planet, including its core, is cooling. If condensed-matter scientists can determine the present-day temperature of the Earth’s core and the thermal conductivity of iron, “we can estimate how …