Probing Ancient Biosignatures: Laser Mass Spectrometric Analysis of the 3.33 Ga Josefsdal Chert Using Laboratory and Space-prototype Instrumentation

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Abstract The search for extraterrestrial life is a major driver of current space exploration, requiring sensitive instrumentation and a thorough understanding of biosignature preservation. Studying terrestrial analogs provides insights into the types of biosignatures preserved in early terrestrial rocks at a period when life may have flourished at the surface of Mars. Here, we investigate the 3.33 Ga Josefsdal Chert from the Barberton Greenstone Belt, South Africa, a carbonaceous chert containing presumed traces of early life, using laser ablation ionization mass spectrometry (LIMS). Chemical analyses were carried out with both a high-resolution laboratory instrument and a compact space-prototype, designed for the in situ chemical composition analysis of solids on solar system objects. LIMS was used to characterize the element composition and its spatial distribution in carbonaceous laminations and clots. These were previously identified by optical microscopy and Raman spectroscopic mapping and considered to be potential biosignatures. LIMS found these features to be enriched in biorelevant elements, such as CHNOPS as well as biologically important transition metals, thus supporting a biogenic origin of the studied organic material of the Josefsdal Chert. The combined approach of the two instruments strengthens confidence in the results and demonstrates the potential of LIMS for future space exploration and sample return missions and the in situ identification of biosignatures.

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