A Pilot Search for Evidence of Extrasolar Earth-analog Plate Tectonics

TL;DR

This study investigates the potential evidence of Earth-like plate tectonics on extrasolar rocky planets by analyzing elemental ratios in white dwarf accretions, finding limited signs of crustal material indicative of tectonic activity.

Contribution

It re-examines spectral data to set upper bounds on crustal elemental signatures, providing a novel approach to detecting Earth-analog tectonics beyond our solar system.

Findings

Limited evidence of crustal enrichment in white dwarf accretions

Most pollution likely from non-tectonic planetary material

Method establishes upper bounds for tectonic signatures

Abstract

Relative to calcium, both strontium and barium are markedly enriched in Earth's continental crust compared to the basaltic crusts of other differentiated rocky bodies within the solar system. Here, we both re-examine available archived Keck spectra to place upper bounds on n(Ba)/n(Ca) and revisit published results for n(Sr)/n(Ca) in two white dwarfs that have accreted rocky planetesimals. We find that at most only a small fraction of the pollution is from crustal material that has experienced the distinctive elemental enhancements induced by Earth-analog plate tectonics. In view of the intense theoretical interest in the physical structure of extrasolar rocky planets, this search should be extended to additional targets.