Why choose lipid biomarkers for the search of life

Molecular biomarkers are natural products that can be assigned to a particular biosynthetic origin. One key aspect to be considered a good biomarker guy is the potential for preservation over time. Lipids are structural components of cell membranes that fulfill successfully this requirement, being amongst the most recalcitrant structural biopolymers able to resist for billions of years upon mild diagenesis. This makes them excellent candidates for tracing biosignatures and past environmental changes in ancient samples. In addition, they may be combined with their compound-specific isotope analysis, gaining specificity about biological sources and further obtaining insights into autotrophic metabolisms. This way, the combined molecular and isotopic analysis of lipid biomarkers arise as a powerful forensic tool able to provide unique “fingerprints” of biosynthetic pathways, organismic sources, environmental conditions, and alteration extent. For all these reasons and mostly because of their high resistance to degradation, lipid molecules have been considered one of the target compounds to pursue in astrobiological missions (e.g. ExoMars) devoted to the search of extraterrestrial life (e.g. GC-MS based MOMA instrument).