{"id":240053,"date":"2026-09-05T08:22:37","date_gmt":"2026-09-05T08:22:37","guid":{"rendered":"https:\/\/www.europesays.com\/be-fr\/240053\/"},"modified":"2026-09-05T08:22:37","modified_gmt":"2026-09-05T08:22:37","slug":"how-mercury-formed-its-graphite-crust-and-core","status":"publish","type":"post","link":"https:\/\/www.europesays.com\/be-fr\/240053\/","title":{"rendered":"How Mercury formed its graphite crust and core"},"content":{"rendered":"

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\"A<\/p>\n

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image:\u00a0<\/p>\n

The young planet was characterised by a global magma ocean and a liquid metallic core, before cooling and differentiating to acquire its current internal structure.<\/p>\n

view more\u00a0<\/a><\/p>\n

Credit: University of Li\u00e8ge \/ B.Charlier<\/p>\n

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 Li\u00e8ge<\/a> and KU Leuven<\/a> 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\u2019s core, the crystallisation of its magma ocean and the formation of its mantle.<\/p>\n

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 disc 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 crystallises, 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.<\/p>\n

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, in order to reconstruct the planet\u2019s history, scientists draw on a specialised 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 analyse the minerals, metals and gases that make up the planet\u2019s various layers.<\/p>\n

It was by employing these techniques that the teams led by Bernard Charlier<\/a> (ULi\u00e8ge) and Olivier Namur <\/a>(KULeuven) carried out an extensive series of high-pressure, high-temperature experiments (at temperatures of between approximately 1,250 and 2,170 \u00b0C)\u00a0 and at pressures equivalent to those found deep within the planets, in order to simulate and track the behaviour of carbon during the separation of the metallic core from the silicate magma of the mantle.\u00a0<\/p>\n

Carbon that changes sides depending on the conditions…<\/p>\n

From the results obtained, the teams were able to deduce that the behaviour of carbon depended heavily on the oxidation state of the environment, as measured by the oxygen fugacity (fO2 ). \u201cUnder relatively oxidising conditions, carbon is strongly siderophile,\u201d explains Bernard Charlier, a geologist at ULi\u00e8ge. \u201cIn other words, carbon prefers metal and therefore enters the core. But under the highly reducing conditions specific to Mercury, it becomes much less siderophile (attracted to metal), and so remains in the silicate magma, where it eventually crystallises as graphite.\u201d<\/p>\n

Based on these experiments, the team reconstructed how carbon was distributed between Mercury\u2019s core, mantle, crust and primitive atmosphere. By comparing these results with the thickness of the graphite crust calculated from data from the MESSENGER probe, they were able to determine the conditions that prevailed during the planet\u2019s formation \u2013 undoubtedly an environment extraordinarily low in oxygen.<\/p>\n

… and a graphite crust formed by flotation<\/p>\n

\u201cUnder these extreme conditions, graphite is too light to sink; it floats on the surface of the magma ocean and accumulates to form a primitive crust,\u201d adds Olivier Namur, also a geologist. The model reproduces a graphite crust approximately 40 to 120 metres thick, consistent with the carbon-rich layer (1 to 3 per cent by mass) that observations attribute to Mercury\u2019s surface.\u201d This primordial crust would then have been disrupted and redistributed by meteorite impacts and by the volcanism that built the planet\u2019s more recent crust.<\/p>\n

MESSENGER\u2019s geodetic data also indicate that the exceptionally large core (accounting for around 70 per cent of the planet\u2019s mass) must contain several per cent of light elements to account for its density deficit. \u201cCarbon had been proposed as a candidate,\u201d continues Olivier Namur. \u201cHowever, under the very conditions that allow the graphite crust to form, the study shows that the core remains low in carbon \u2013 less than 5,000 micrograms per gramme, or less than 0.5 per cent. Such a concentration is far too low to account for the observed deficit.\u201d<\/p>\n

It is therefore primarily silicon and, to a lesser extent, sulphur that must constitute the light elements of the core. These elements have another property: they significantly lower the melting point of iron, which could explain why Mercury\u2019s core has remained at least partially liquid for 4.5 billion years \u2013 a characteristic necessary to sustain its magnetic field.\u00a0<\/p>\n

By linking Mercury\u2019s extreme chemical reduction to both its graphite crust and the structure of its core, this research provides a useful framework for understanding other highly reduced bodies: the original, more massive proto-Mercury; the hypothetical \u2018super-Mercuries\u2019; certain carbon-rich exoplanets, and also the early Earth, which was largely built from reduced materials. \u201cFuture observations, notably by missions such as BepiColombo, could confirm and quantify graphite as a major phase on Mercury\u2019s surface,\u201d concluded Bernard Charlier.<\/p>\n

Journal<\/p>\n

Nature Communications<\/p>\n

Article Title<\/p>\n

Carbon distribution in planet Mercury from magma ocean evolution to graphite crust and core composition<\/p>\n

Article Publication Date<\/p>\n

28-Aug-2026<\/p>\n

Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.<\/p>\n","protected":false},"excerpt":{"rendered":"image:\u00a0 The young planet was characterised by a global magma ocean and a liquid metallic core, before cooling…\n","protected":false},"author":2,"featured_media":240054,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_share_on_mastodon":"0"},"categories":[70],"tags":[12,13,18,17,73,71,75,72,76,74],"class_list":["post-240053","post","type-post","status-publish","format-standard","has-post-thumbnail","category-sciences-et-technologies","tag-be","tag-be-fr","tag-belgique","tag-belgium","tag-science","tag-science-and-technology","tag-sciences","tag-sciences-et-technologies","tag-technologies","tag-technology"],"share_on_mastodon":{"url":"https:\/\/pubeurope.com\/@be_fr\/117217470011077690","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/be-fr\/wp-json\/wp\/v2\/posts\/240053","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/be-fr\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/be-fr\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/be-fr\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/be-fr\/wp-json\/wp\/v2\/comments?post=240053"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/be-fr\/wp-json\/wp\/v2\/posts\/240053\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/be-fr\/wp-json\/wp\/v2\/media\/240054"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/be-fr\/wp-json\/wp\/v2\/media?parent=240053"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/be-fr\/wp-json\/wp\/v2\/categories?post=240053"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/be-fr\/wp-json\/wp\/v2\/tags?post=240053"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}