Uv Radiation-Induced PET Degradation: Unveiling Organic Degradation Indicators via Raman Spectroscopy for Martian Research

Understanding the expected evolution of organic molecules in the environment of Mars holds significant scientific importance, as it is a crucial aspect of the Mars 2020 and other Mars exploration missions, ultimately aimed to identify biosignatures on the Martian surface. The Martian environment, characterised by UV radiation and specific climatic conditions, presents challenges for the preservation of organic molecules, as they can undergo structural degradation, leading to altered characteristics and hindering their detection. The SuperCam Calibration Target (SCCT) plays a key role in the SuperCam instrument, serving for calibration and evaluation purposes, but also to monitor the effect the Martian environment on organic materials. Polyethylene terephthalate (PET), an organic polymer, is included as part of the calibration samples in the SCCT. By studying the degradation of PET caused by UV radiation and the Martian atmospheric conditions, researchers can gain valuable insights into the stability of organic matter when subject to the Martian environment. To provide supportto address thisquestion, this studyfocuseson replicating the climatic conditions of the Martian surface in a laboratory setting to evaluate the extent of PET degradation caused by UV radiation as a function of ambient temperature. Specifically, potential variations in Raman spectral measurements induced by UV radiation are monitored. Different Ertalyte ® PET samples (similar to the SCCT PET) from the same batch have been irradiated for different time intervals and at three distinct temperatures (-50ºC, - 20ºC, and 0ºC). The results show changes in the signal-to-noise ratio (SNR), with higher radiation doses resulting in lower SNRs, also showing a certain correlation between degradation and temperature. In addition, changes in the fluorescence profile indicate the influence of radiation and ageing on the properties of organic molecules. Therefore, the laboratory experiments investigating the ageing of PET samples under simulated Martian conditions are critical for understanding how UV radiation and the environment affect the preservation of organic molecules on Mars. Combining data obtained from SuperCam with these laboratory studies could potentially provide a more comprehensive approach to the processes affecting organic matter and potential biomarkers of ancient life on Mars, thereby facilitating the work of Mars2020 data interpretation as well as paving the way for future missions and advances in planetary science.