Recent research suggests that “super-Earths,” which are planets larger than Earth but smaller than Neptune, may have a natural defense against harmful radiation. This finding raises interesting possibilities about the potential for life on these worlds.
Super-Earths are frequently found in the habitable zones of their stars, where conditions could allow for liquid water. Understanding if these planets can support life-friendly environments over billions of years is crucial for scientists.
The study proposes that many super-Earths could generate strong magnetic fields from molten rock located not in their cores, like Earth, but in a layer between the core and mantle. According to Miki Nakajima, the lead researcher and professor at the University of Rochester, “A strong magnetic field is vital for life on a planet.” These planetary dynamos, if created from magma, could enhance the habitability of super-Earths.
Published in *Nature Astronomy,* the findings address a puzzling question: How can super-Earths maintain magnetic fields when their interiors differ from Earth’s? Luca Maltagliati, a senior editor at *Nature Astronomy,* noted that these planets might produce magnetic fields not from a solid or liquid core, but from a unique layer in their interiors.
Long-lasting magnetic shields are essential for protecting a planet’s atmosphere from being stripped away by stellar winds, as well as shielding surfaces from harmful cosmic and solar radiation. Without this protection, even planets in favorable habitable zones could struggle to maintain life-sustaining conditions. Thus, these magma-driven magnetic fields may be key to the potential habitability of super-Earths across the galaxy.
Earth’s magnetic field has been operational for over 3 billion years, generated by the movement of liquid iron in its outer core. However, super-Earths may have different core structures, which usually limits traditional magnetic field generation. Nakajima and her team highlight a process called a basal magma ocean (BMO), a layer of molten rock believed to form between the core and mantle during a planet’s formation. This could sustain magnetic fields for longer periods, especially under the immense pressures found in larger planets.
Super-Earths might sustain these magma layers, allowing for stronger magnetic fields that could endure for billions of years. To test this idea, the team conducted shock experiments simulating the extreme pressures of these massive planets. They found that under such conditions, iron-rich magma becomes metallic and electrically conductive, which could enable super-Earths three to six times the mass of Earth to maintain potent magnetic fields that rival or exceed Earth’s.
The researchers believe it’s possible to observe these strong BMO-driven dynamos in future studies, even though detecting exoplanet magnetic fields remains a challenge.
This research opens the door to a deeper understanding of super-Earths and their potential for life. As we explore the cosmos, these findings encourage us to rethink what we consider habitable worlds.
