Mercury Explained: Understanding Its Iron Core and the Sun's Magnetism

A recent study is challenging the prevailing hypothesis on why Mercury has a bigger core relative to the planet's mantle. Scientists, for decades, have argued that the hit-and-run collisions on other celestial bodies during the early days of the solar system blew off much of Mercury's rocky mantle leaving only its big, dense, metal core. However, new research reveals that collisions are not as much to blame as the Sun's magnetism

Mercury Explained

Mercury, the planet nearest to the sun and the smallest planet in the solar system are only slightly bigger than the Earth's moon. From its surface, the sun appears to be three times larger than how its viewed on Earth with the sunlight radiating seven times brighter.

Contrary to popular belief and its proximity to the sun, Mercury is not the hottest planet in the solar system. This title rightfully belongs to Venus, mostly due to its dense atmosphere.

According to NASA, a day on Mercury takes roughly 59 Earth days. Where the planet completes an orbit around the Sun in 88 Earth days. Compared to Earth, Mercury has a thin atmosphere composed primarily of oxygen, sodium, helium, hydrogen, and potassium.

An interesting fact about Mercury is that it has no satellites or moons. No evidence of life has ever been observed in the planet whose daytime temperatures can reach 430 degrees Celsius and drop to 180 degrees Celsius below 0.

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Understanding Mercury's Iron Core and How the Sun's Magnetism Affected it

William McDonough, lead author, and a geology professor at the University of Maryland, Takeshi Yoshizaki from the Tohoku University developed a density, mass, and iron content model of the rocky planet's core that was influenced by the distance between the planet and the sun's magnetic field.

The paper published in the journal Progress in Earth and Planetary Science, entitled "Terrestrial planet compositions controlled by accretion disk magnetic field" describes how the model challenges conventional hypothesis on Mercury's mantle and core composition.

McDonough explains that the four inner planets of the solar system — Mercury, Venus, Earth, and Mars — consist of varying proportions of rock and metal. A gradient exists where the metal contents in the planet's core drop off as each planet gets farther from the Sun. The paper explains how the phenomenon occurred by showing the distributions of raw materials during the early days of the solar system when the Sun's magnetic field controlled the formation.

The model shows how during the early days of the solar system, when the young sun was engulfed in swirling clouds of gas and dust, grains of iron were dragged towards the Sun's magnetic field. As the planets began to form from the clumps of dust and gas, planets closer to the sun began to incorporate more of the iron into their respective cores than those that were formed farther away.

The research found that the proportion and density of iron on Mercury's core correlate with the strength of the sun's magnetic field during planetary formation reports Phs.Org.

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Mercury Explained: Understanding Its Iron Core and the Sun's Magnetism