Physicists have taken a significant step toward unraveling one of the most profound enigmas in geophysics: the origin of the Earth’s magnetic field.
A team of researchers from the University of Texas at Austin, in collaboration with scientists from Sichuan and Nanjing Universities in China, believes they have unearthed a fundamental physical mechanism that can help elucidate the surprisingly “soft” characteristics of the Earth’s dense inner core.
Deep within the Earth, approximately 1,800 miles beneath the crust, resides a spherical core primarily composed of iron and nickel. This core, with temperatures ranging from about 8,000 to 10,800 degrees Fahrenheit, consists of two layers: the liquid outer core and the dense, solid inner core. The movement of iron atoms within this core is understood to power the Earth’s magnetic field, a vital element in rendering the planet habitable. This magnetic field not only establishes compass directions but also acts as a protective shield, deflecting potent radiation from solar storms.
Although the Earth’s magnetic field is primarily generated in the liquid outer core through the convective motion of molten metal, the role of the solid inner core in this geodynamo process has remained an enigma. “Earth’s core is under such extreme pressures of ~ 3.5 Mbar (3.5 million times atmospheric pressure), so one would think that iron atoms are so confined to their positions and there’s not much wiggle room for them to move,” explains Jung-Fu Lin, a professor at the University of Texas Jackson School of Geosciences and one of the leading authors of the study. “What we found was totally against this traditional view.”
To unveil this mystery, the team reconstructed a miniature model of the Earth’s inner core within a laboratory setting. The objective was to predict the properties and behavior of iron atoms within this extreme environment. What they discovered was profoundly unconventional: instead of remaining stationary in their solid lattice, the iron atoms were in rapid motion.
This phenomenon, termed collective motion in physics, can be likened to guests at a dinner party swapping seats without altering the overall arrangement of the table. In the words of Lin, “The iron atoms were wiggling their way so fast that they moved to other positions in a split second.”
This finding, which challenges conventional wisdom, sheds light on the “soft” properties of the Earth’s inner core, presenting potential insights into the generation of heat at the planet’s core. Furthermore, it enhances our understanding of the processes that underpin the Earth’s magnetic field and may offer insights into the inner workings of other planets within and beyond our solar system.
Lin expounds, “The discovery implies that the same physics of collective motion may occur in other planetary interiors, such as Mars and exoplanetary interiors. Exoplanets endure even more extreme pressure and temperature conditions, so further research is needed to determine if this phenomenon occurs there. This will contribute to our comprehension of planetary systems on a broader scale.”
By Impact Lab