Due to its magnetic properties, Mercury's massive central core is predominantly composed of iron.

New Study Challenges Traditional View of Mercury's Large Core

A new study published on July 2, 2021, in the journal Progress in Earth and Planetary Science has disputed the prevailing hypothesis on Mercury's large core. The research, titled "Terrestrial planet compositions controlled by accretion disk magnetic field," was conducted by William McDonough from the University of Maryland and Takashi Yoshizaki from Tohoku University.

The study presents a new model for the formation of the core composition of Earth-like planets. According to this model, the sun's magnetism, not collisions, is responsible for Mercury's big, dense, metal core. This finding contradicts the current belief that Mercury's large core is the result of violent collisions with other celestial bodies during its formation.

The composition of a planet's core is important for its potential to support life, as seen on Earth where a molten iron core creates a magnetosphere that protects the planet from cancer-causing cosmic rays. The new research suggests that each planet's iron content could be influenced by the magnetic properties of the star during the early growth of the solar system.

McDonough's new model shows that during the early formation of our solar system, planets closer to the sun incorporated more iron into their cores than those farther away. This gradient in metal content and density corresponds perfectly with what scientists know about the planets in our solar system. For instance, Mercury has a metallic core that makes up about three-quarters of its mass, while the cores of Earth and Venus are only about one-third of their mass, and Mars, the outermost of the rocky planets, has a small core that is only about one-quarter of its mass.

The University of Maryland College of Computer, Mathematical, and Natural Sciences is the institution where the research was conducted. If the density of the planets drops as they radiate out from the sun, as it does in our solar system, this would support the new theory. The research paper was published on July 2, 2021, and can be accessed using the DOI 10.1186/s40645-021-00429-4.

This new understanding of the role magnetism plays in planetary formation creates a challenge in the study of exoplanets, as there is currently no method to determine the magnetic properties of a star from Earth-based observations. For media inquiries, please contact Kimbra Cutlip at [email protected]. The University of Maryland College of Computer, Mathematical, and Natural Sciences educates over 9,000 future scientific leaders each year.

To confirm this new theory, scientists need to find another planetary system like ours, with rocky planets spread over wide distances from their central sun. This discovery could provide further evidence for the new model and deepen our understanding of planetary formation and the potential for life beyond our solar system.