By C. J. De Mel, Jadetimes News
Mercury, the closest planet to the Sun, remains one of the least understood bodies in our Solar System. Composed similarly to Earth and other rocky planets with silicate minerals and metals, Mercury stands out due to its unusually large core, comprising a significant portion of its mass. Adding to its intrigue, Mercury possesses a persistent magnetic field that has puzzled scientists for years, making it one of the most captivating planets in the Solar System.
Recent research suggests Mercury may be even more fascinating than previously thought. A collaborative study by Chinese and Belgian geoscientists has unveiled evidence of a solid diamond layer beneath Mercury's crust. According to their simulations, this diamond layer, approximately 15 km (9 mi) thick, lies sandwiched between the core and mantle, hundreds of miles beneath the surface. Although these diamonds are currently inaccessible, the findings have profound implications for our understanding of the formation and evolution of rocky planets.
The international team, comprising researchers from the Center for High Pressure Science and Technology Advanced Research, China University of Geosciences, KU Leuven, and the University of Liege, published their findings in Nature Communications. Their work was inspired by prior research from MIT, NASA’s Goddard Space Flight Center, and other prominent institutions. This earlier research reassessed Mercury’s gravity field using radio tracking data from NASA’s MESSENGER mission, providing new insights into Mercury’s internal structure, including a metallic outer core layer, a liquid core layer, and a solid inner core.
While the core's exact composition remains uncertain, it likely contains abundant iron, nickel, silicon, and possibly sulfur and carbon. The MESSENGER data indicated that large dark patches on Mercury’s surface are primarily graphite, suggesting significant carbon crystallization in the planet's interior. This led to the hypothesis that Mercury might be saturated with carbon. Previously, the formation of diamond was considered unlikely due to insufficient pressure near Mercury’s core. However, if the core mantle boundary is deeper than previously thought, the necessary pressure conditions might exist.
The research team used thermodynamic modeling to recreate these conditions, hypothesizing a deeper core mantle boundary. Their simulations indicated that with a sulfur content around 11% and pressures at 1-2% of those in Earth's interior, diamond could crystallize within Mercury's molten core. They proposed that this diamond would form a stable layer, rising along with graphite towards the mantle. Over eons, this diamond layer could reach a thickness of 15 to 18 km (9 to 11 mi).
Diamond, being an excellent thermal conductor, could significantly impact our understanding of Mercury's interior dynamics and its magnetic field. The way heat transfers from the core influences the cooling and evolution of rocky planets, and internal material movement is crucial for generating magnetic fields. Mercury, the only rocky planet besides Earth with a magnetosphere, may have a magnetosphere older than Earth's. Revised models of Mercury’s interior could explain the longevity of its magnetosphere, with broader implications for theories on the formation and evolution of rocky planets in our Solar System.
Mercury’s potential diamond layer beneath its crust adds a new dimension to our understanding of this enigmatic planet. The findings not only enhance our knowledge of Mercury’s internal structure but also offer new perspectives on the dynamics and evolution of rocky planets.
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