BIOSIGNATURE DETECTION IN THE ATACAMA DESERT, CHILE

The Northern Atacama Desert, Chile, is known to be one of the most arid and oldest deserts in the world.  Claims have been made that the driest areas in this desert have only low levels of viable organisms and the harsh conditions make it a possible analog for the surface of Mars.  We have developed an ultra-sensitive method for detection of amino acids and nucleobases in collaboration with the University of California at Berkeley, NASA/Caltech JPL, and the Scripps Institution of Oceanography to determine if it is possible to detect low-level biosignatures of extant or extinct life in the Atacama. The Mars Organic Laboratory (MOL) used in the field-testing consists of two stages.  The first stage is the Sub-Critical Water Extractor (SCWE) which extracts organics, including amino acids, from the soil via steady-state flow of high-pressure, high-temperature water.  The second stage is the analytical portion of the instrumentation, the Micro-Capillary Electrophoresis detector (μ-CE).  This compact, portable instrument provides the benefits of high sensitivity (5x10^-20 moles), nanoliter size injections, and chiral resolution of amino acids.  The extremely low detection limits are achieved through laser-induced fluorescence after reaction with fluorescamine.  Representative field results from the μ-CE are shown below: the two fractions are sequential SCWE extractions at 250°C for 2 minutes on the same soil.

 

AT40B2_08	Valine	Alanine/Serine	Glycine
Fraction (i)	14.2	47.3	90.9
Fraction (ii)	5.5	19.1	34.3

All values reported in ppb. Sample collection was focused on a pristine hill near the Yungay experimental station in the Atacama Desert (S24°03.629'; W69°52.092').  Samples were collected from a variety of geologically unique microenvironments around the hill, and each site was sampled in a depth transect.  Studies on a sample subset included analyses for amino acid biosignatures at the research station and post-field work included analysis for total organic carbon and nitrogen, stable carbon and nitrogen isotopic ratios, amino acids, nucleobases, and microbial culture experiments.  This field trial demonstrated the successful detection of amino acid biomarkers from the driest, most Mars-like environment in the Atacama Desert.  Detailed results of the field and laboratory studies will be presented.