期刊
ASTROBIOLOGY
卷 18, 期 4, 页码 431-453出版社
MARY ANN LIEBERT, INC
DOI: 10.1089/ast.2017.1716
关键词
Raman spectroscopy; Laser-induced fluorescence spectroscopy; Mars Sample Return; Mars 2020 mission; Kerogen; Biosignatures
资金
- NASA Astrobiology Institute (NAI) Early Career Collaboration Award
- NASA Mars exploration Program
- Natural Sciences and Engineering Research Council of Canada (NSERC)
- Postdoctoral Fellowship at Carnegie Institution for Science
The Mars 2020 mission will analyze samples in situ and identify any that could have preserved biosignatures in ancient habitable environments for later return to Earth. Highest priority targeted samples include aqueously formed sedimentary lithologies. On Earth, such lithologies can contain fossil biosignatures as aromatic carbon (kerogen). In this study, we analyzed nonextracted kerogen in a diverse suite of natural, complex samples using colocated UV excitation (266nm) time-gated (UV-TG) Raman and laser-induced fluorescence spectroscopies. We interrogated kerogen and its host matrix in samples to (1) explore the capabilities of UV-TG Raman and fluorescence spectroscopies for detecting kerogen in high-priority targets in the search for possible biosignatures on Mars; (2) assess the effectiveness of time gating and UV laser wavelength in reducing fluorescence in Raman spectra; and (3) identify sample-specific issues that could challenge rover-based identifications of kerogen using UV-TG Raman spectroscopy. We found that ungated UV Raman spectroscopy is suited to identify diagnostic kerogen Raman bands without interfering fluorescence and that UV fluorescence spectroscopy is suited to identify kerogen. These results highlight the value of combining colocated Raman and fluorescence spectroscopies, similar to those obtainable by SHERLOC on Mars 2020, to strengthen the confidence of kerogen detection as a potential biosignature in complex natural samples.
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