• Le 28 August 2019

At 2060 km across, the core of planet Mercury is 50 km larger than we believed up to now. This discovery was made by three researchers from the Laboratoire de planétologie et géodynamique (CNRS / Université de Nantes / Université d’Angers). Their results, published in early August in the Journal of Geophysical Research – Planets, shed some light on the mystery of Mercury before the arrival of the BepiColombo mission to arrive near the planet in 2025

The radius of the core therefore accounts for 85% of the planet’s radius !

But how did the researchers from Laboratoire de planétologie et géodynamique (CNRS / Université de Nantes / Université d’Angers) succeed in calculating the size of Mercury’s core? This was made possible by studying data on the planet’s magnetic field collected by the American probe Messenger. Indeed, when the magnetic field around Mercury changes due to the influence of solar wind(¹), its core generates what is known as an induced response, proportional to the external field, but also to its size, which it is then possible to deduce.


(1) A flux of protons that the Sun emits continuously in all directions. As on Earth, the solar wind interacts with the magnetic field of Mercury’s dynamo to create a dynamic magnetosphere, which generates a magnetic field at the exterior of the planet.


Mission spatiale BepiColombo © ESA/ATG medialab, NASA/JPL
Mission spatiale BepiColombo © ESA/ATG medialab, NASA/JPL