Magma oceans and enhanced volcanism on TRAPPIST-1 planets due to induction heating

TL;DR

This study investigates how electromagnetic induction heating caused by stellar magnetic fields can lead to magma oceans and increased volcanism on TRAPPIST-1 planets, especially the innermost ones, affecting their geological states.

Contribution

It introduces the concept that induction heating due to star-planet magnetic interactions can significantly influence planetary volcanism and magma ocean formation.

Findings

Inner planets may develop magma oceans due to induction heating.

Induction heating increases volcanic activity and outgassing.

Outer planets remain largely unaffected.

Abstract

Low-mass M stars are plentiful in the Universe and often host small, rocky planets detectable with the current instrumentation. Recently, seven small planets have been discovered orbiting the ultracool dwarf TRAPPIST-1\cite{Gillon16,Gillon17}. We examine the role of electromagnetic induction heating of these planets, caused by the star's rotation and the planet's orbital motion. If the stellar rotation and magnetic dipole axes are inclined with respect to each other, induction heating can melt the upper mantle and enormously increase volcanic activity, sometimes producing a magma ocean below the planetary surface. We show that induction heating leads the three innermost planets, one of which is in the habitable zone, to either evolve towards a molten mantle planet, or to experience increased outgassing and volcanic activity, while the four outermost planets remain mostly unaffected.