Decoding Signs of Life

Abstract

The search for extraterrestrial life relies fundamentally on the identification of robust biosignatures, a pursuit facilitated by studying the metabolic emissions of terrestrial organisms under extreme environmental conditions. To this end, this study evaluates the empirical detection limits of primary metabolic gases (such as CO2 and H2O alongside trace biogenic volatile organic compounds (VOCs) released by microorganisms subjected to severe environmental stresses, specifically a nitrogen-rich atmosphere and an oxidative environment. Using a gas-phase modular, closed-system Fourier-transform infra-red (FT-IR) spectroscopy system, discrete VOCs are monitored to observe the metabolic shifts of Saccharomyces cerevisiae (commonly known as Brewer's yeast) and Cylindrotheca fusiformis (a marine diatom). Prioritization was given to well-resolved spectral features, with distinct fluctuations in CO2 and water vapour H2O serving as real-time indicators of cellular degradation. Yeast cells exhibited stress responses in both environments, whereas C. fusiformis appeared unaffected by the nitrogen-rich atmosphere but was severely degraded by oxidative stress. Although visual morphological changes were present, this paper primarily focuses on the systemic vulnerabilities of discrete sampling frameworks when mapping transient gas-generation bursts. By serving as a controlled terrestrial analogue, these experiments provide critical data to understand how biological trace gases might behave and degrade in extreme extraterrestrial environments. This study discusses these observational limitations within the broader framework of remote planetary sensing. Ultimately, characterizing dynamic gas fluctuations serves a dual purpose: refining theoretical models of exoplanetary atmospheres and aiding the search for preserved, relic biogenic signals within the solar system.