New Analytical Methodology to Reveal Biosignatures on Mars and Ocean Worlds

Abstract

Terrestrial analog environments and their microbial communities are key elements to prepare for the exploration of extraterrestrial planetary environments that potentially sustained, or even may still sustain, the (bio)chemistry necessary for life to emerge. Characterization of terrestrial analogue environments reveals information on the distribution of (i) biomolecules produced by life as we know it and (ii) biomolecules potentially preserved and associated with ancient life (e.g., lipids). We developed and validated a new untargeted method to detect biomolecules that can be applied to both laboratory and in situ-space-based research to extract and detect biomolecules and/or biosignatures using gas chromatography coupled to mass spectrometry (GC–MS). The method consists of a one-pot reaction using a chemical reagent to enhance organic matter extraction and volatilization. The novelty of the study was based on the selection of temperature and time of reactivity to extract the wider range of organic molecules and led to the following optimal sample preparation conditions for nonstandard samples: (i) DMF-DMA at 300 °C for 1–3 min, (ii) MTBSTFA at 150 °C for 1–15 min, or (iii) TMAH at 600 °C for 1–30 s. This approach was first validated through investigation of biomolecules from two pure cultures of extremophiles (Chroococcidiopsis cubana cyanobacteria and Halobacterium salinarum halophilic archaea) to detect them in analog environments (the dry American Pilot Valley desert and the Icelandic Gunnuhver hot spring) that have been explored as analogs of Mars and likely ocean world surfaces, respectively. Our findings showed that this untargeted method inhibits the loss of organic matter and contamination compared to multistep extraction and purification in classical methods and benefit explorations by the current Curiosity rover at Mars. The method can be implemented in portable GC–MS in the field or used by spaceflight instrumentation to detect parts per trillion (ppt) to ppt of wide diversity of (bio)molecules (e.g., amino acids, carboxylic/fatty acids, alcohols/sugars, nucleic acids, etc.) and C,O,N,S-bearing compounds trapped in a geological matrix.