An Overview of Lipid Biomarkers in Terrestrial Extreme Environments with Relevance for Mars Exploration

Abstract

Lipid molecules are organic compounds, insoluble in water, and based on carbon-carbon chains that form an integral part of biological cell membranes. As such, lipids are ubiquitous in life on Earth, which is why they are considered useful biomarkers for life detection in terrestrial environments. These molecules display effective membrane-forming properties even under geochemically hostile conditions that challenge most of microbial life, which grants lipids a universal biomarker character suitable for life detection beyond Earth, where a putative biological membrane would also be required. What discriminates lipids from nucleic acids or proteins is their capacity to retain diagnostic information about their biological source in their recalcitrant hydrocarbon skeletons for thousands of millions of years, which is indispensable in the field of astrobiology given the time span that the geological ages of planetary bodies encompass. This work gathers studies that have employed lipid biomarker approaches for paleoenvironmental surveys and life detection purposes in terrestrial environments with extreme conditions: hydrothermal, hyperarid, hypersaline, and highly acidic, among others; all of which are analogous to current or past conditions on Mars. Although some of the compounds discussed in this review may be abiotically synthesized, we focus on those with a biological origin, namely lipid biomarkers. Therefore, along with appropriate complementary techniques such as bulk and compound-specific stable carbon isotope analysis, this work recapitulates and reevaluates the potential of lipid biomarkers as an additional, powerful tool to interrogate whether there is life on Mars, or if there ever was.

Origin and modern microbial ecology of secondary mineral deposits in Lehman Caves, Great Basin National Park, NV, USA

“…Gypsum and other sulfate minerals are of special interest to astrobiologists as targets for past or present life detection, particularly on Mars, which has abundant sulfate deposits (Benison & Karmanocky, 2014;Finkel et al, 2023). Caves are an attractive setting to explore the microbial ecology and biosignature preservation potential of gypsum because dark, subterranean settings are removed from photosynthetic inputs that can overwhelm biomarker detection (Johnson et al, 2020).…”

Chiroptical properties of membrane glycerophospholipids and their chiral backbones

“…Even though complex glycerophospholipids have not been identified in any extraterrestrial material thus far, the detection of their precursors is a significant advancement in this research avenue and offers important insights for targeting lipids as chiral biomarkers in the quest for past and/or present life in space. In particular, lipids have been selected as one of the key molecules to be searched for as part of the ExoMars 2028 mission to Mars due to their great longevity over geological timescales, which is at least an order of magnitude longer than that of RNA/DNA, proteins, or amino acids' ee 30,31 …”

“…In particular, lipids have been selected as one of the key molecules to be searched for as part of the ExoMars 2028 mission to Mars due to their great longevity over geological timescales, which is at least an order of magnitude longer than that of RNA/DNA, proteins, or amino acids' ee. 30,31…”

Designing a novel method based on multiplex PCR for detecting various meat of birds in processed ground meat products

“…The current techniques for determining the authenticity of meat depend on lipid, protein, and nucleic acid indicators ( Piri Gharaghie and Sadat Shandiz, 2018 ). Lipid-biomarkers, which contain both the sort and amount of lipids, may experience significant changes during the preparation of meals, whereas protein-biomarkers are vulnerable to physio-chemical shocks ( Finkel et al, 2023 ). However, tiny DNA biomarkers, in particular, are very robust in a deteriorated environment.…”