The Sun’s magnetism gave Mercury its huge iron core

Mercury is only a third the size of the Earth. How, then, did he get such a gargantuan iron core, at least for its size?

The reason why the core of Mercury is so huge has been cheated until now. Scientists believed it was born from a series of massive collisions at the start of the solar system, the culprits being other objects that destroyed much of the smaller planet’s surface and left it with a metallic core as well. important and dense. Now, a new study has found that it was the Sun’s intense magnetism that pulled iron particles through the protoplanetary cloud in which Mercury was forming.

Solar magnetism explains why embryonic planets that developed closer to the Sun billions of years ago took more of its iron into their nuclei. Geologists William McDonough from the University of Maryland and Takashi Yoshizaki from the University of Tohoku in Japan studied this and recently published a study in Advances in Earth and Planetary Sciences. Existing models of planetary formation helped them determine the rate at which gas and dust were drawn to the center of the nascent solar system.

“The speed of gas and dust will vary with time and place in an accretion system,” McDonough told SYFY WIRE in an interview. “As the material is attracted to the gravitational center, its speed will increase due to the ever-increasing gravitational pull. This is because the combined forces of the proto-Sun are growing and matter is approaching the Sun and thus detects its gravitational field. “

It was the Sun’s magnetic field that controlled the raw materials floating in the early universe. Our star and surrounding planets emerged from a protoplanetary disk of gas and dust, eventually settling into prograde orbits (east-to-west as opposed to retrograde) and occasionally falling in shared rotation. It can take up to 10 million years for the dust from the protoplanetary disks to dissipate, which is still quite fast in cosmic terms. The physical and chemical properties of the disc change with it, including the makeup of the star or stars and planets within.

What McDonough and Yoshizaki discovered is that there is a gradient of iron content in the planetary cores of the solar system, with most iron in Mercury’s core, gradually decreasing as you move away from it. Venus from Earth to Mars. Less and less iron is found in the planets beyond. All that iron swirled around the protoplanetary disk to begin with. The Sun’s powerful magnetic field continued to attract grains of this iron towards it, and the nuclei of the planets that formed in its immediate vicinity picked up more of this iron than bodies further away.

There were other elements that often joined the iron particles that stuck together to form the core of a planet. Most of the phosphorus on Earth, 90%, is found in its core. “It’s really a matter of the differences in the processes controlled by physics versus chemistry,” he said. “Metal particles are attracted to electromagnetic forces because of the electric field they create by the shapes of their electronic orbits. The iron-nickel particles can be considered as ferro-magnets. The phosphorus is incorporated into the forming metallic phase which condenses out of the solar nebula.

Magnetism is something that could not be measured before in exoplanets by observing them from land. Instead, scientists would study the spectrum of the star around which these planets orbit to see what that star was made of based on the wavelengths of radiation it emitted. It was then assumed that the planets of the star system in question were probably made of the same material. What McDonough discovered means that the makeup of exoplanets depends on the magnetic properties of their star.

Determining how much iron each planet should have based on the amount in their star could have huge implications not only for discovering the makeup of distant planets, but also their potential to harbor life. core of the earth is 80 percent iron. Its liquid outer core acts as a geodynamo which provides a magnetic field that protects us from the killer cosmic rays and other forces in space that continue to bombard Mars. The Martian the magnetic field is weak because Mars doesn’t have an internal dynamo to create one strong enough to fight whatever it is exposed to.

“Magnetism is to be viewed in the future as a force controlling the makeup of a planet,” McDonough said.

If something lived on Mars it probably went extinct, and if something lives there it might not be anything like life as we know it. Did Mercury ever have life? No one knows, but magnetism could one day help scientists find habitable planets.


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