Far below the surfaces of distant rocky exoplanets known as super-earths, vast layers of molten rock may be performing a remarkable role. These hidden reservoirs could generate magnetic fields strong enough to protect entire planets from cosmic radiation and other high-energy particles.
On Earth, the magnetic field comes from motion in the planet’s liquid iron outer core, a process called a dynamo, but larger rocky planets may not operate the same way. Some super-earths could have cores that are either solid or entirely liquid, limiting their ability to produce magnetic fields through this familiar mechanism.
In a paper published in Nature Astronomy, researchers at the University of Rochester, including Miki Nakajima, an associate professor in the Department of Earth and Environmental Sciences, describe a different source. They point to a deep layer of molten rock known as a basal magma ocean (BMO). This idea could change how scientists understand planetary interiors and may influence how they assess whether distant worlds can support life.
“A strong magnetic field is very important for life on a planet,” Nakajima says, “but most of the terrestrial planets in the solar system, such as Venus and Mars, do not have them because their cores don’t have the right physical conditions to generate a magnetic field. However, super-earths can produce dynamos in their core and/or magma, which can increase their planetary habitability.”
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