Introduction
Hypersaline lakes and coastal brines are today’s best terrestrial analogues for Martian bodies of water. In particular, columns of magnesium sulfate (Mg-SO4) brines and sulfate-rich salt deposits present chemical settings that resemble deposits inferred on Mars. This study evaluates how lipid biosignatures—such as fatty acids, alkanes, and ether-bound lipids—are produced and preserved in modern Mg-SO4–rich lakes and their sediments, and what this implies for detecting past life on Mars or other rocky worlds.
Methods and Settings
Researchers surveyed modern brines, salt deposits, and surface sediments from several lakes on the Cariboo Plateau of British Columbia, Canada. The lakes studied include Last Chance Lake, Salt Lake, and multiple Basque Lake sites. Analyses focused on lipid biomarkers (short- and long-chain fatty acids, n-alkanes, and ether-bound lipids), total organic carbon (TOC), carbon/nitrogen (C/N) ratios, and bulk isotopes (δ13C and δ15N) to contextualize biosignatures with overall carbon pools and sources.
Key Lipid Findings
Across all lakes, the predominant biosignatures are short-chain fatty acids (C<23), which align with microbial production pathways. Sediments show a broader lipid assemblage, including microbially derived and terrestrially derived lipids. Notably, ether-bound lipids, characteristic of archaea and some bacteria, constitute a minor yet measurable fraction of the lipid pool in brines. This pattern contrasts with many NaCl-dominated brines, where archaeal biomass often dominates the lipid signal.
Organic Carbon and Isotopic Context
TOC concentrations in sediments span from 0.7% to 12%, with sulfate-rich sediments at the higher end. This richness suggests substantial preservation potential for microbial lipids within these environments. Isotopic analyses support these conclusions: δ13C values and C/N ratios point to aquatic microbial inputs as primary carbon sources, rather than exclusively terrestrial contributions. The combination of abundant microbial lipids and favorable isotopic signatures strengthens the case for in situ biosignatures persisting in sulfate-rich settings.
Implications for Mars and Life Detection
Compared with Cl-dominated Mars-analog sites that show limited organic matter production, and acidic, sulfate-rich environments dominated by terrestrial inputs, Mg-SO4-rich hypersaline lakes emerge as prolific reservoirs for biosignatures. High TOC, coupled with lipid diversity and in situ microbial production markers, indicates robust preservation potential over geological timescales. If these processes were active on early Mars, Mg-SO4-rich settings could have preserved biosignatures in mineral matrices for extended periods, aiding future life-detection missions to identify ancient habitability and biosignature deposits.
Broader Significance
The study underscores the need to prioritize Mg-SO4-rich environments in the search for preserved organics on Mars and similar worlds. The presence of short-chain fatty acids and archaeal lipids, even at low abundances, can serve as robust biosignature indicators when coupled with high TOC and characteristic isotopic patterns. Moreover, the results suggest that ancient sulfate-rich basins, if preserved, might retain a richer biomarker record than more chloride-dominated or acidic analogues.
Site Map and Visual Context
The study includes a map and aerial photographs of the Cariboo Plateau lakes, illustrating contemporary hypersaline systems that mirror Martian-like chemistry. The images emphasize natural, unaltered color palettes and ecosystems, reinforcing the real-world relevance of these environments as analog sites.
Conclusion
Mg-SO4-rich hypersaline lakes host a robust microbial lipid biosignature landscape and display strong preservation potential in sediments. Their organic richness and isotopic coherence with aquatic microbial sources position them as leading terrestrial analogues for assessing the feasibility of long-term biosignature preservation on Mars. This work informs targeted search strategies for lipid biomarkers in Martian samples and highlights the value of integrating lipidomics with bulk geochemistry to interpret past habitability.
Acknowledgments and Visual Credits
Map and aerial photos from the Cariboo Plateau lakes were captured by field teams and contribute to the geographic context of these modern analogues.
