View in EDS

Magnetic Evolution of Super‐Earth Exoplanets With a Basal Magma Ocean.

Saved in:
Bibliographic Details
Title: Magnetic Evolution of Super‐Earth Exoplanets With a Basal Magma Ocean.
Authors: Lherm, Victor1,2,3 (AUTHOR) victor.lherm@cnrs.fr, Nakajima, Miki2,3 (AUTHOR), Blackman, Eric G.3 (AUTHOR)
Source: Journal of Geophysical Research. Planets. Mar2026, Vol. 131 Issue 3, p1-19. 19p.
Subject Terms: Magnetic fields, Planetary interiors, Extrasolar planets, Earth's mantle, Magnetohydrodynamics, Habitable planets
Abstract: Habitability of super‐Earths likely requires self‐sustained magnetic fields to shield their atmospheres from stellar forcing. Extreme pressures and temperatures probably produce a long‐lived basal magma ocean (BMO), a potential source for these fields. To determine when the magnetic field is primarily powered by a BMO rather than a convective core, we examine the structural, thermal, buoyancy, and magnetic evolution of super‐Earths involving a coupled core, BMO, and mantle. We find that more massive planets host larger BMOs with prolonged, stronger silicate dynamos, that increasingly overlap with core dynamos, but produce stronger fields. In contrast, planets with larger cores have shorter‐lasting silicate dynamos, resulting in dominant core fields. Using a conservative electrical conductivity, we predict that silicate dynamos are likely sustained in super‐Earths, except in low‐mass planets with large cores. Strong silicate dynamos could facilitate the detection of magnetic fields on super‐Earths, constraining their internal structure and potential habitability. Plain Language Summary: Among rocky planets larger than Earth, known as "super‐Earths," some might be able to sustain life if they generate strong enough magnetic fields to protect against atmospheric mass loss from the effects of stellar winds and radiation. Inside these planets, the combination of extreme temperatures and pressures can create a layer of molten rock at the base of the mantle, called a "basal magma ocean," where these fields may be powered, in addition to any field production that may occur in the planet cores. We find that larger super‐Earths have large basal magma oceans that can support long‐lasting magnetic fields typically stronger than those powered in the planet's core. In contrast, planets with larger cores lose their basal magma ocean faster, leaving only the magnetic fields produced in the core. From estimates of how well molten rocks conduct electricity, we find that most super‐Earths will likely sustain magnetic fields from a basal magma ocean, except for smaller ones with disproportionately large cores. Detecting such fields outside our solar system could offer clues about the interiors of these planets and their potential ability to support life. Key Points: In increasingly massive super‐Earths, the stronger silicate dynamos powered in larger basal magma oceans increasingly dominate core dynamosIn planets with larger core mass fractions, the core dynamos increasingly dominate shorter‐lasting silicate magma ocean dynamosSilicate dynamos are likely sustained in super‐Earths, except in low‐mass planets with large cores preventing their activity [ABSTRACT FROM AUTHOR]
Copyright of Journal of Geophysical Research. Planets is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
Database: GreenFILE
Description
Abstract:Habitability of super‐Earths likely requires self‐sustained magnetic fields to shield their atmospheres from stellar forcing. Extreme pressures and temperatures probably produce a long‐lived basal magma ocean (BMO), a potential source for these fields. To determine when the magnetic field is primarily powered by a BMO rather than a convective core, we examine the structural, thermal, buoyancy, and magnetic evolution of super‐Earths involving a coupled core, BMO, and mantle. We find that more massive planets host larger BMOs with prolonged, stronger silicate dynamos, that increasingly overlap with core dynamos, but produce stronger fields. In contrast, planets with larger cores have shorter‐lasting silicate dynamos, resulting in dominant core fields. Using a conservative electrical conductivity, we predict that silicate dynamos are likely sustained in super‐Earths, except in low‐mass planets with large cores. Strong silicate dynamos could facilitate the detection of magnetic fields on super‐Earths, constraining their internal structure and potential habitability. Plain Language Summary: Among rocky planets larger than Earth, known as "super‐Earths," some might be able to sustain life if they generate strong enough magnetic fields to protect against atmospheric mass loss from the effects of stellar winds and radiation. Inside these planets, the combination of extreme temperatures and pressures can create a layer of molten rock at the base of the mantle, called a "basal magma ocean," where these fields may be powered, in addition to any field production that may occur in the planet cores. We find that larger super‐Earths have large basal magma oceans that can support long‐lasting magnetic fields typically stronger than those powered in the planet's core. In contrast, planets with larger cores lose their basal magma ocean faster, leaving only the magnetic fields produced in the core. From estimates of how well molten rocks conduct electricity, we find that most super‐Earths will likely sustain magnetic fields from a basal magma ocean, except for smaller ones with disproportionately large cores. Detecting such fields outside our solar system could offer clues about the interiors of these planets and their potential ability to support life. Key Points: In increasingly massive super‐Earths, the stronger silicate dynamos powered in larger basal magma oceans increasingly dominate core dynamosIn planets with larger core mass fractions, the core dynamos increasingly dominate shorter‐lasting silicate magma ocean dynamosSilicate dynamos are likely sustained in super‐Earths, except in low‐mass planets with large cores preventing their activity [ABSTRACT FROM AUTHOR]
ISSN:21699097
DOI:10.1029/2025JE009447