Citation:
Catherine S. Rix, Mark R. Sims, and David C. Cullen. Immunological detection of small organic molecules in the presence of
perchlorates: relevance to the life marker chip and life detection on Mars. Astrobiology, 2011,
Volume 11, Number 9, pp839-846
Abstract:
The proposed ExoMars mission, due to launch in 2018, aims to look for evidence
of extant and extinct life in martian rocks and regolith. Previous attempts to
detect organic molecules of biological or abiotic origin on Mars have been
unsuccessful, which may be attributable to destruction of these molecules by
perchlorate salts during pyrolysis sample extraction techniques. Organic
molecules can also be extracted and measured with solvent-based systems. The
ExoMars payload includes the Life Marker Chip (LMC) instrument, capable of
detecting biomarker molecules of extant and extinct Earth-like life in liquid
extracts of martian samples with an antibody microarray assay. The aim of the
work reported here was to investigate whether the presence of perchlorate salts,
at levels similar to those at the NASA Phoenix landing site, would compromise
the LMC extraction and detection method. To test this, we implemented an LMC-
representative sample extraction process with an LMC-representative antibody
assay and used these to extract and analyze a model sample that consisted of a
Mars analog sample matrix (JSC Mars-1) spiked with a representative organic
molecular target (pyrene, an example of abiotic meteoritic infall targets) in
the presence of perchlorate salts. We found no significant change in immunoassay
function when using pyrene standards with added perchlorate salts. When model
samples spiked with perchlorate salts were subjected to an LMC-representative
liquid extraction, immunoassays functioned in a liquid extract and detected
extracted pyrene. For the same model sample matrix without perchlorate salts, we
observed anomalous assay signals that coincided with yellow coloration of the
extracts. This unexpected observation is being studied further. This initial
study indicates that the presence of perchlorate salts, at levels similar to
those detected at the NASA Phoenix landing site, is unlikely to prevent the LMC
from extracting and detecting organic molecules from martian samples.
