Optimizing a novel life detection technique for life detection in Mars analog soils from the Atacama desert
A key goal of astrobiology is to determine how to unambiguously detect signs of life beyond Earth. The diversity of organic molecules detected on Mars and in martian meteorites suggests that conditions to support life may exist or once have existed near the martian surface. Surface conditions from the Amazonian (2.9 Ga) to today are inhospitable to most forms of life known on Earth, but halophilic (i.e., salt-loving) microbes may be an exception. Future robotic missions to Mars and other rocky bodies will need analytical techniques that can distinguish between fossil (extinct) and extant microbial biosignatures.
We propose to apply lipid hydrogen stable isotope probing (LHSIP) to detect the activity of extant microbes in the Atacama Desert salt flats, a robust analog for modern Mars. LHSIP couples the identification of lipid biosignatures with measuring the incorporation of a stable H-isotope tracer into specific lipid structures, which only occurs if microbes are active. LHSIP can distinguish lipids synthesized by extant life from preserved, fossil lipids. Because lipids are produced by all domains of life on Earth and H is incorporated into all known biomolecules, LHSIP is taxa-agnostic and well-suited to detect microbial life in virtually any environment.
In this study we will test the LHSIP method on soils collected from five Atacama salars that span a gradient in mean annual temperature (7 to 18°C) and potential evaporation (1000 to 1800 mm yr-1). This project will aid the search for extant life beyond Earth by: (1) field-testing and calibrating an extant life-detection technique that is well-suited for environments with low organic content and slow microbial growth, and (2) defining specific environmental niches within martian salt-rich highlands or crustal dichotomy, most likely to host conditions necessary for life. These near-surface salt deposits are a compelling target in the search for extant life due to the relative ease with which rovers can access them. If the LHSIP technique is successful in Mars analog sites, the method should then be tested at analogs for other promising targets for detecting life beyond Earth (e.g., Europa, Enceladus, Titan).