Chemical gardens mimic electron paramagnetic resonance (EPR) spectra and morphology of biogenic Mn oxides

Sigrid Huld, Sean McMahon, Susanne Sjoberg, Ping Huang, Anna Neubeck

Research output: Contribution to journalArticlepeer-review

Abstract

Manganese oxides are ubiquitous in nature and occur as both biological and
abiotic minerals, but empirically distinguishingbetween the two remains a
problem. Recently, electron paramagnetic resonance (EPR) spectroscopy has
been proposed for this purpose. It has been reported that biogenic Mn
oxides display a characteristic narrow linewidth in contrast to their pure abiotic
counterparts, which is explained in part by the large number of cation vacancies that form within the layers of biogenic Mn oxides. It was therefore proposed that natural samples that display a narrow EPR linewidth, ΔHpp < 580G, could be assigned to a biogenic origin. However, in poorly crystalline or amorphous solids both dipolar broadening and exchange narrowing simultaneously determine the linewidth. Considering that the spectral linewidth is governed by several mechanisms, this approach might be questioned. Here, we report synthetic chemical garden Mn oxide biomorphs that exhibit both morphologically life-like structures and narrow EPR linewidths, suggesting that a narrow EPR line may be unsuitable as reliable evidence in assessment of biogenicity.
Original languageEnglish
JournalAstrobiology
Publication statusAccepted/In press - 1 Aug 2022

Keywords

  • Mn oxides, EPR, chemical gardens, biomorphs

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