Chemical identification of microfossils from the 1.88‐Ga Gunflint chert: Towards empirical biosignatures using laser ablation ionization mass spectrometer

Rustam A Lukmanov,Peter Wurz,Andreas Riedo,Coenraad De Koning,Valentine Grimaudo,David Wacey,Niels F W Ligterink,Marek Tulej,Anna Neubeck

doi:10.1002/cem.3370

Abstract

AbstractIn this contribution, we investigated the chemical composition of Precambrian microfossils from the Gunflint chert (1.88 Ga) using a miniature laser ablation ionization mass spectrometer (LIMS) developed for in situ space applications. Spatially resolved mass spectrometric imaging (MSI) and depth profiling resulted in the acquisition of 68,500 mass spectra. Using single mass unit spectral decomposition and multivariate data analysis techniques, we identified the location of aggregations of microfossils and surrounding inorganic host mineral. Our results show that microfossils have unique chemical compositions that can be distinguished from the inorganic chert with high fidelity. Chemical depth profiling results also show that with LIMS microprobe data, it is possible to identify chemical differences between individual microfossils, thereby providing new insights about nature of early life. Analysis of LIMS spectra acquired from the individual microfossils reveals complex mineralization, which can reflect the metabolic diversity of the Gunflint microbiome. An intensity‐based machine learning model trained on LIMS Gunflint data might be applied for the future investigations of putative microfossils from silicified matrices, where morphological integrity of investigated structures is lost, and potentially in the investigation of rocks acquired from the Martian surface.

Highlights

IntroductionIn situ research and remote sensing have provided multiple lines of evidence that clement conditions were present on the surface of early Mars.[1,2,3] recent radar studies reveal evidence of subglacial liquid water on Mars,[4] which supports the hypothesis that microbial life forms (extinct or extant) may be preserved within the Martian subsurface.[4,5]
The distribution of microfossils embedded in a quartz matrix is shown with gray lenticular structures
Locations of microfossils were identified on the surface of the sample utilizing mass spectrometric imaging (MSI)

Summary

Introduction

In situ research and remote sensing have provided multiple lines of evidence that clement conditions were present on the surface of early Mars.[1,2,3] recent radar studies reveal evidence of subglacial liquid water on Mars,[4] which supports the hypothesis that microbial life forms (extinct or extant) may be preserved within the Martian subsurface.[4,5]. All these observations provide a strong rationale for the search of biosignatures on the Red Planet. The current state of space exploration provides foundation for new measurement techniques and novel analytical approaches[6] to identify and characterize minerals and potential signatures of life, if any, on Mars.

Methods

Results

Conclusion