Hidden in plain sight? Some challenges and needs for practical planetary biosignature exploration, both home and away-A Mini-Review.

Stephen Larter, Ben Tutolo, Christopher Tino, Lloyd Snowdon, Renzo Silva, Haiping Huang

Identifying organic molecular biosignatures for life is challenging. Most current analytical methods were developed on Earth sediments rich in total organic carbon (TOC), and these methods struggle when dilute organic matter is situated within reactive, mineralogically complex astrobiological samples. Diverse geological alteration processes degrade biomarker signals, often concealing some chemical structures within hybrid species. Thermal maturation destroys biomarker chirality and primary molecular signatures at moderate burial temperatures (≤150 °C). Radiolysis, diagenesis, and maturation can eliminate reactive species and produce both lower and complex higher molecular weight products that may retain partial biological structures that are likely analytically obscured. Detecting low concentrations of such molecular biosignature structures hidden in composite reaction products presents a promising research focus. Selecting samples for return missions is crucial, necessitating an effective field screening system to assess organic carbon content and thermal history in potentially low TOC samples. Enhanced automated image-based detection of microbial structures, such as stromatolite analogs, is also a promising avenue for technological advancement, as is searching for gas transportable, resilient molecular markers, such as adamantanes, at seep locations.