22-EPN3-026: Life detection and biosignature preservation studies via lipid biomarker analysis in Makgadikgadi Salt Pan
Visit by Pablo Finkel and Laura Sánchez García (Centro de Astrobiología (CAB), CSIC-INTA, Spain) to TA1.5 Makgadikgadi Salt Pans (Botswana).
Dates of visit: 02-09 October 2023
In large evaporitic basins such as the Makgadikgadi Salt Pans in Botswana, a series of strategies that promote the long-term preservation of lipids take place in its immediate subsurface: protective mineral-organics interactions, halite encapsulations within matrices, salt-derived enzymatic inhibition, cellular adaptations, and entombment by chemical precipitation of minerals. These strategies, plus the high preservation potential of lipid biomarkers, crafts a recipe for optimism in regard to the state of the lipids found in Makgadikgadi, whose degradation may be effectively attenuated as their preservation is enhanced.
The main goal of this project was to collect different types of samples from the pans to characterise their lipid biomarker content to a) identify biological (molecular and isotopic) features and b) to assess lipid preservation and/or degradation. Samples with protective matrices suitable for organics preservation include halite crusts, xero-mineral matrix and silcretes from Sua Pan, as well as silcretes, calcretes and mineral precipitates found in inverted channels from a relict delta. More humid samples where these protective features may lack included surface and subsurface soil samples from concentric layered mounds believed to have formed under a water table. Nonethless, these mounds present a geomorphological analogy to the Equatorial Layered Deposits (ELD) on Mars, and given the infiltrating capillary fringe that render the Makgadikgadi mounds humid, a similar process on Mars could establish the ELDs as habitable refugia. In the laboratory, once the lipid profile of all samples is characterised, the team will proceed with irradiation studies to challenge lipid degradation in protective versus non-protective matrices.
Read the full scientific report with kind permission by Pablo Finkel and Laura Sánchez García.