The quest to discover life remains a fundamental objective of Mars exploration. During its early geological history, Mars hosted substantial volumes of surface liquid water, leading to the development of diverse water-related sedimentary deposits. However, as the planet's climate evolved, it gave way to the extreme present-day environment—marked by aridity, low temperatures, strong oxidative conditions, and high levels of radiation. Central scientific challenges include evaluating how well biosignatures could be preserved within these ancient aqueous environments under such harsh conditions, and investigating the potential existence of life-related evidence in the Martian subsurface. Moreover, numerous nodular features identified in Gale Crater—believed to have formed in neutral to alkaline, saline diagenetic fluids—remain to be thoroughly examined for their implications in astrobiology.

Located in the northern Tibetan Plateau of northwest China, the Qaidam Basin ranks among the world's largest and driest deserts. Owing to its wide range of desiccated aqueous deposits and landforms that bear strong resemblance to Martian terrains, it serves as a significant terrestrial analog for Mars (Shen et al., 2022). This research investigates the spatial distribution and environmental drivers of shallow subsurface microbial ecosystems (Chen et al., 2023a), the presence of organic compounds in fluvio-lacustrine sediments and surface soils (Chen et al., 2022), and the potential for biosignature preservation in carbonate nodules found in this Mars-analogous setting (Chen et al., 2023b; Chen et al., 2024). Findings indicate that microbial life is most prevalent at depths between 5 and 25 cm, with a marked decline in abundance both nearer the surface and deeper underground under extreme arid conditions. Key sites such as ancient lakebeds and alluvial fans are identified as priority zones for the search for Martian life. Additionally, the nodular formations discovered in Gale Crater may offer favorable conditions for biosignature retention in hyperarid environments, assuming life once developed there. Spectroscopic techniques, including Raman and Fourier-transform infrared spectroscopy, are emphasized as critical for biosignature detection and the analysis of Martian returned samples. These results offer important guidance for identifying promising exploration sites and refining instrument payload designs for future Mars missions.
 

Biosignatures