Looking for life in the UV: fluorescence as a tool for planetary exploration

Whether or not the Solar System has provided environments conducive to microbial life beyond Earth is a major focus of current space exploration. This endeavour is driven by the identification of a great diversity of extraterrestrial environments, such as ancient lakes on Mars and subsurface oceans on the icy moons of Jupiter. Investigating the habitability of these environments requires new tools and technology to be developed. These can then be used to detect mineral deposits that are indicative of either past or present habitable environments, identify any organic material preserved within them, and establish whether or not those organics were produced by life or not. 

This project will investigate how to use UV fluorescence imaging to detect and characterise different mineral substrates and organic inclusions trapped within them, with the aim to develop this technique for use in future planetary exploration by in situ landers and rovers. 

UV fluorescence – the emission of visible light following UV irradiation – is a well-exploited phenomenon within the material and biological sciences, and a technique that has just started to be fully harnessed in planetary exploration. However little is currently known about the fluorescent ‘fingerprints’ of the minerals, organic molecules, and biosignatures that will likely be found in these extraterrestrial environments, and the best techniques to detect them. This includes the precise spectrum of the fluorescence emitted by a sample, the best UV wavelength with which to excite the strongest fluorescence response, and the effect of heterogenous samples on the resulting fluorescence fingerprint. Such information is vital if we are to successfully interpret datasets sent back from robotic spacecraft, and design new instruments for future missions. 

We will investigate the UV fluorescent fingerprints of combined mineral and organic material, using state-of-the-art facilities at Aberystwyth University and the University of St. Andrews. These facilities will characterise the UV fluorescence response of mineral and organic samples at temperatures comparable to those on Mars and icy moons such as Europa. We will use two types of samples for our work – the first will be mineral and organic samples that are created experimentally in the laboratory under carefully-controlled conditions. These will allow us to precisely establish what fluorescence fingerprints are produced and why. The second will be natural samples collected from environments on Earth that are analogous to those on Mars and elsewhere. These will provide ‘realistic’ samples with which to test and understand this technique. Finally, we will feed this knowledge into the scientific development of novel planetary lander instrument prototypes that will hopefully play an important role in future space exploration. 

Dr Claire Cousins
University of St Andrews

Both images are of sulfate mineral samples ~1 cm in size, as seen under UV illumination (credit Matt Gunn).