THE UREY INSTRUMENT SUITE - STATUS AND FUTURE IMPLEMENTATION

Urey is an advanced instrument suite that has been selected for in situ organic and oxidant detection on future Mars exploration missions. The organic detector consists of 3 subsystems, the Sub-Critical Water Extractor (SCWE), Mars Organic Detector (MOD), and µ-Capillary Electrophoresis instrument (µ-CE). The Mars Oxidant Investigation (MOI) has the capability to independently characterize oxidants within both the atmosphere and regolith. Currently, miniature versions of each component instrument exist as validated field-test units. The Urey flight-instrument has been engineered and a functional full-scale (~7,000 cm³) prototype will be completed within 2 years.

The organic detection system utilizes a 2-stage extraction procedure which first liberates organic compounds from the soil or regolith sample using high-temperature high-pressure water (SCWE). Target organics are then isolated via sublimation onto a cold finger (MOD). The analytical system is configured around the µ-CE instrument which separates and analyzes fluorescamine-labeled primary amine compounds. The target amines include several of the major molecular species ubiquitous in terrestrial life such as amino acids, amino sugars, and nucleobases. Naturally fluorescent PAHs can also be separated and quantified.

The high sensitivity of the µ-CE system and efficiency of SCWE extraction allow for detection of amino acids from biodensities of ~10³ cells/g in 60mg of sample. The capability of the Urey instrument to detect chiral amino acids will allow discrimination between abiotic formation and biosynthesis by an extant or extinct Martian biota. If proteins and amino acids have been degraded, Urey can resolve various amine decarboxylation products. The cold and dry climate of Mars should have minimized diagenesis of biological materials in the near-surface regolith, allowing biosignature preservation on geological timescales if the samples were adequately protected from radiolysis. Urey has been selected as part of the Pasteur payload for the 2013 ESA ExoMars mission. The proposed drilling capabilities of the ExoMars Rover will allow for the greatest chance of success in the detection of biomolecules characteristic of terrestrial life.