A Surface Plasmon Resonance-based instrument for the detection of extraterrestrial life

The subject of this thesis is work relating to the design and testing of the Specific Molecular Identification of Life Experiments, SMILE – a family of Life Marker Chip-type devices currently being developed to search for signs of life on other planets, notably Mars. The SMILE devices will be capable of conducting bioassay measurements on Martian soil samples using molecular receptors to detect target organic molecules (biomarkers). One version of SMILE intends to use the phenomenon of Surface Plasmon Resonance (SPR), combined with fluorescence detection, to probe the sample for biomarkers indicative of the presence of life on the planet, past or present. The main work described in this study falls into two areas; the first is that relating to the design, construction and initial testing of a breadboard demonstrator of combined SPR-Fluorescence detection to understand the practical problems associated with such a system. A theory for the SPR response was developed and fitted to experimental data gathered from the demonstrator with good agreement. The detection of bound analyte via SPR imaging and simultaneous fluorescence imaging was successfully demonstrated. The second part of the thesis describes initial radiation damage tests on fluorescent labelling molecules of the type intended for use in the Life Marker Chip bioassay. The fluorophores were exposed to proton, alpha and gamma radiation at fluences and doses equivalent to those expected for representative mission scenarios. All tested samples survived expected mission fluences, but some effects were detected at higher fluences/doses. Samples were also tested in both desiccated and solute forms, with desiccation found to be preferable for increased radiation tolerance. Lessons learnt from the work are explained, and future work required to progress to a flight version of the SMILE instrument is described.