Development of an optical sensor for in situ detection of biosignatures in icy moons

Hydrothermal vents are considered the most promising environments for the origin of life on Earth, as their chemical and thermal gradients may have driven the synthesis of the first protocell structures. Similar conditions are thought to exist in the subsurface oceans of icy moons in the Solar System, where access to internal material is partially enabled by cryovolcanic plumes. Optical sensors represent a promising solution for evaluating habitability in such environments through in situ detection of chemical signatures. They enable sensitive environmental monitoring over a wide range of conditions, while maintaining compact and low-power designs that are compatible with the requirements of future space missions. This thesis presents the development of a fluorescence-based optical sensor at the Spin.Works company for the detection of environmental parameters relevant to the assessment of biosignatures on icy moons, as part of the Origin of Life: from Hydrothermal Vents to Protocells (ORIGINS) project. The sensor architecture is based on a membrane producing fluorescence under ultraviolet excitation. The emitted signal is collected through a wavelength-selective optical system and detected by a photomultiplier tube. The fluorescence decay dynamics are modulated by quenching effects driven by environmental variables, including temperature and gas concentration, enabling indirect characterisation of the surrounding medium. A predictive model was developed, describing the variation of the fluorescence lifetime under different conditions. Preliminary experimental results provide a first validation of the sensitivity of the instrumental response to temperature variations, supporting further development and optimisation. The proposed approach demonstrates the potential of fluorescence-based sensing for in situ characterisation of potentially habitable environments in future space exploration missions, including upcoming programmes of the European Space Agency (ESA).