A thick layer of diamonds could be hidden beneath Mercury’s surface

Mercury, the planet closest to the Sun, may be hiding a treasure beneath its inhospitable surface: a layer of diamond. Recent research and modeling suggests that the carbon on Mercury could have transformed into diamond under extreme conditions of pressure and heat. This fascinating discovery could not only shed more light on the formation of this small planet, but also on the evolution of rocky planets in general.

Conditions favorable to the formation of diamonds

Scientists have long speculated about the composition and evolution of Mercury, the smallest planet of the solar system. Data collected by the MESSENGER space probe revealed an abundance of graphite on its surface, suggesting a crucial role of carbon from the earliest stages of the planet’s formation. However, the implications of this discovery have long remained uncertain. More recently, advanced models have explored for the first time the possibility that this carbon underwent spectacular transformations under the influence of the intense heat of Mercury’s ancient magma ocean. Researchers have discovered that extreme pressure and temperature conditions in Mercury’s mantle and core may have played a crucial role in the carbon to diamond conversion. The extremely high pressure, combined with temperatures reaching nearly 2,000°Cin fact creates an ideal environment for carbon reorganizes into a crystalline structureThese discoveries thus suggest that Mercury, despite its small size and extreme environment, could shelter a diamond layer beneath its surfacepotentially several kilometers thick.
Credits: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Challenges and future prospects

Despite these intriguing findings, several questions remain about the formation and preservation of diamonds on Mercury. Researchers are considering two main scenarios: the formation of diamonds from the initial magma ocean, possibly rich in sulfurOr their expulsion from the core during its solidification. Each of these scenarios presents its own challenges and implications for our understanding of Mercury’s geological history. The first hypothesis assumes that during Mercury’s magmatic phase, a significant amount of sulfur would have been present in its magma ocean. This presence of sulfur could have altered the chemistry of the environment, making diamond formation possible on a large scale. However, even with an abundance of sulfur, the production of diamonds in substantial quantities remains uncertain and may depend on very specific geological conditions. The second scenario suggests that diamonds may have been expelled from Mercury’s core during its crystallization. As the planet’s inner core solidified, carbon would have been released in the form of diamond, potentially forming a significant layer between the core and the silicate mantle. This could explain the presence of diamonds on a planet as small as Mercury, despite the comparatively low pressure and gravity conditions compared to Earth. Both scenarios raise fundamental questions about Mercury’s unique geological processes and offer avenues for future research and exploration of the planet. Understanding the formation and occurrence of diamonds on Mercury could not only shed light on our understanding of terrestrial planets, but also enrich our knowledge of the evolution of planetary systems near the Sun. Furthermore, the electrical conductivity of diamonds could play a crucial role in maintaining Mercury’s magnetic field, a key aspect for understanding the planet’s interaction with the solar wind and the surrounding space environment. To advance our understanding of this hypothetical diamond layer, the scientists plan to continue their studies using more detailed models and future exploration missions. Details of the study are published in the journal Nature Communications.