Font size:
Print
Earth’s Inner Core & the Role of Carbon
Earth’s inner core exists only because of carbon
Context: A recent study by researchers from the University of Oxford, Leeds, and University College London has revealed a groundbreaking insight: Earth’s inner core exists only because of carbon. This discovery reshapes our understanding of planetary formation and the chemistry that sustains life on Earth.
What is core?
Earth’s core is the innermost layer of the planet, divided into:
- Outer Core – Liquid layer (~2,900–5,100 km depth), made mostly of molten iron and nickel.
- Inner Core – Solid sphere (~5,100–6,371 km depth), composed primarily of iron, with lighter elements (O, Si, S, C).
What is the significance of core?
- Geomagnetism: The outer core’s molten iron generates Earth’s magnetic field through the geodynamo effect. Protects life on Earth by deflecting harmful solar radiation and cosmic rays.
- Geothermal Energy: Heat flow from the core drives mantle convection, volcanism, and plate tectonics.
- Seismic Studies: Earthquake waves (P- and S-waves) provide insights into the density, state (solid/liquid), and composition of the core.
- Evolution of Earth: The solidification of the inner core contributes to the planet’s long-term cooling, stability of the magnetic field, and habitability.
What is the significance of carbon in Earth’s core?
- Core Crystallisation: The study shows that 3.8% carbon allows freezing of the inner core at only 266 °C supercooling, consistent with observations. Without carbon, the required supercooling (~800–1000 °C) is unrealistic → inner core may never have formed.
- Density Deficit Explanation: Seismology shows the core is less dense than pure iron. The presence of carbon (a lighter element) helps explain this density gap.
- Magnetic Field Stability: A properly crystallised core ensures a steady growth of the inner core → sustains the geodynamo → stable magnetic field over geologic timescales.
- Chemical Evolution: Suggests that carbon, a volatile element, sank into the core during Earth’s differentiation. Provides a rare clue to the deep-Earth carbon cycle and how volatiles shaped planetary formation.
- Planetary Comparisons: May explain why Earth developed a stable inner core (and magnetic shield) while other planets (e.g., Mars) lost theirs.
