Mercury, known as the smallest and fastest planet in our solar system, may also hold a glittering secret. New research suggests that this celestial body, the closest planet to the Sun, could harbour a layer of diamonds beneath its crust, potentially stretching kilometres deep.
This fascinating theory emerged from data collected by NASA’s MESSENGER spacecraft, which spent 11 years orbiting Mercury and mapping its entire surface. During its mission, MESSENGER discovered abundant water ice in shadowed regions at the poles and revealed that much of Mercury’s surface consists of graphite.
The distribution of this graphite led planetary scientists to conclude that carbon was present during Mercury’s formation, rather than being delivered by comets or asteroids, as reported by IFL Science.
Research insights
Dr. Yongjiang Xu from China’s Center for High-Pressure Science and Technology Advanced Research has been exploring what happened to all that carbon during Mercury’s early days when the planet differentiated into its core and crust.
The researchers hypothesize that Mercury contained even more carbon in its infancy, which decreased over time as gases like carbon dioxide and methane escaped from its molten surface. In their paper published in Nature Communications, Xu and his colleagues state, “The abundance of graphite in the Mercurian crust indicates that the planet remained saturated in a carbon phase during metal-silicate differentiation, core formation, and the entirety of magma ocean crystallization.” In essence, a significant amount of carbon persisted as the planet’s magma ocean solidified into the rocky surface we see today. However, carbon alone does not create diamonds—immense pressure is also required.
Diamond formation scenarios
The researchers propose two potential scenarios for the formation of Mercury’s diamond layer. The first suggests that diamonds were produced directly by the magma ocean, but this would have required a substantial amount of sulfur to alter the chemistry sufficiently. Even with abundant sulfur, large-scale diamond production under these conditions is deemed improbable. The second, more likely scenario posits that as Mercury’s solid inner core formed, carbon was expelled, leading to the formation of a diamond layer kilometres thick. High temperatures could have burned the outer parts of this layer, reverting it to graphite, yet much of the diamond could have survived between Mercury’s core and its silicate mantle.
Implications and future research
The conductivity of this diamond layer might even contribute to Mercury’s magnetic field, according to scientists. However, Dr. Bernard Charlier from Belgium’s University of Liège, the study’s senior author, noted that the diamond layer likely does not consist of a single thick shell but rather various chunks. “Let’s be honest,” Dr. Charlier told New Scientist, “We have no idea about the potential size of those diamonds.” This groundbreaking research opens up new possibilities for understanding Mercury’s composition and the dynamic processes that shaped it. As scientists continue to study the data from MESSENGER and future missions, we may uncover more secrets about the innermost planet in our solar system and its potential status as a diamond-rich world.