This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: As the BepiColombo mission prepares to enter the final phase of its journey to Mercury, a series of studies conducted by researchers at the University of Liège and KU Leuven sheds new light on the early stages of the evolution of the planet closest to the sun. Using experimental petrology, the researchers are reconstructing in the laboratory the formation of Mercury's core, the crystallization of its magma ocean and the formation of its mantle.
The studies are published in Earth and Planetary Science Letters, Nature Communications and Advances in Geochemistry and Cosmochemistry. The terrestrial planets (Mercury, Venus, Earth and Mars) are the result of more than four billion years of evolution, which began with accretion from the disk surrounding the young sun. During the early stages of evolution, the heat released caused these planets to melt, creating what is known as a magma ocean.
This key stage determines the distribution of elements between the metallic core and the mantle. As it crystallizes, this ocean structures the solid mantle, the partial melting of which will subsequently generate the magmas that form the crust. It is also at this stage that an initial atmosphere may form.
To date, no samples have been taken from Mercury, and no meteorites have been linked to it. Our knowledge of its composition therefore relies on telescope observations and data from the American probes Mariner 10 (1973) and MESSENGER (2011). However, to reconstruct the planet's history, scientists draw on a specialized discipline: experimental petrology.
This branch of geology enables scientists to reproduce, in the laboratory, the temperatures, pressures and chemical conditions that prevailed inside the planet more than four billion years ago, and then to analyze the minerals, metals and gases that make up the planet's various layers. It was by employing these techniques that the teams led by Bernard Charlier (ULiège) and Olivier Namur (KULeuven) carried out an extensive series of high-pressure, high-temperature experiments. They simulated and tracked the behavior of carbon during the separation of the metallic core from the silicate magma of the mantle at temperatures between approximately 1,250°C (2,282°F) and 2,170°C (3,938°F) and at pressures equivalent to those found deep within the planets.
From the results obtained, the teams were able to deduce that the behavior of carbon depended heavily on the oxidation state of the environment, as measured by the oxygen fugacity (fO2). "Under relatively oxidizing conditions, carbon is strongly siderophile," explains Charlier, a geologist at ULiège. "In other words, carbon prefers metal and therefore enters the core.
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