Deciphering the mysteries of the Earth’s core-mantle boundary (CMB)

Researchers from the SLAC National Accelerator Laboratory and the European Synchrotron Radiation Facility (ESRF) have made progress in deciphering the mysteries of the Earth’s core-mantle boundary (CMB) and the conditions of magma oceans that may exist on super-Earths.

SLAC, part of the U.S. Department of Energy, is a cutting-edge facility specializing in advanced scientific research, while ESRF, located in Grenoble, France, is renowned for its powerful synchrotron X-ray sources. Together, they used high-energy X-ray diffraction techniques to examine molten rock under extreme conditions.

“This study marks a significant advance in our understanding of the Earth’s deep interior,” said collaborator and SLAC senior scientist Arianna Gleason. “The findings underscore the potential of advanced X-ray techniques to reveal the hidden secrets of our planet and beyond.”

The study discovered that altering iron content in molten rock had no significant effect on density, refuting earlier theories about Earth’s creation. 

This finding is significant for understanding how the density difference between crystalline and liquid materials affected planetary evolution.

Understanding the CMB is essential for comprehending how Earth’s geology works and evolves. The barrier, about 2 900 km (1 802 miles) beneath the surface, separates the solid mantle from the liquid outer core.

Information gained from analyzing the CMB can explain processes such as tectonic movements, volcanic activity, and Earth’s magnetic field formation. 

Additionally, the study’s findings on atomic responses to compression could substantially impact the early evolution of super-Earths, which may behave differently than more minor rocky planets such as Earth and Venus.

The investigations and subsequent findings were released as a series of studies in the journal Nature Communications. The study relied on a decade of past research into the characteristics of materials under extreme conditions, culminating in this breakthrough that advances our understanding of planetary innards.

The scientists used high-energy X-ray diffraction techniques at SLAC’s Linac Coherent Light Source (LCLS) to study the behavior of molten rock under severe conditions. 

The breakthrough experiments were principally conducted at SLAC in California and the ESRF in Grenoble, France.

These locations allow scientists to generate intense X-ray beams for examining materials under high-pressure circumstances, broadening the research’s implications for understanding planetary formation and evolution, particularly for exoplanets categorized as super-Earths.

The research team used improved X-ray techniques to simulate circumstances found in super-Earths’ mid to lower mantles, analyzing atomic configurations in molten rock using hard X-rays. 

The scientists also used computer simulations and experimental data to provide a complete understanding of the molten silicates’ characteristics. 

This approach enabled researchers to examine changes in structural properties under extreme conditions, resulting in a better knowledge of silicate behavior. This is important for building accurate models of Earth’s interior and extrapolating to similar conditions on super-Earths.

“Now that we know we can get this quality of data and reach these conditions, we want to push further into exoplanet regimes,” Gleason said. “The ability to generate pressures equivalent to three times Earth’s mantle conditions is exciting. It extends our understanding of silicate properties under extreme conditions, which is crucial for Earth and exoplanet studies.”

A collaborative team of scientists from the Department of Energy’s SLAC National Accelerator Laboratory, led by Guillaume Morard from the University of Grenoble and Sorbonne University in France, has collaborated in this study. 

International experts in high-energy physics also contributed to the research, which extensively used modern X-ray equipment.

References:

¹ Structural evolution of liquid silicates under conditions in Super-Earth interiors – Morard, G., Hernandez, JA., Pege, C. et al. – Nat Commun 15, 8483 (2024) – October 3, 2024 – https://doi.org/10.1038/s41467-024-51796-7 – OPEN ACCESS

² X-rays unlock secrets of Earth’s core-mantle boundary and super-Earth magma oceans – SLAC – October 3, 2024

Harsha Borah

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