Detectability of biosignatures in a low-biomass simulation of martian sediments

Stevens, Adam H.; McDonald, Alison; De Koning, Coenraad Pieter; Riedo, Andreas; Preston, Louisa J.; Ehrenfreund, Pascale; Wurz, Peter; Cockell, Charles S. (2019). Detectability of biosignatures in a low-biomass simulation of martian sediments. Scientific Reports, 9(1) Nature Publishing Group 10.1038/s41598-019-46239-z

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Discovery of a remnant habitable environment by the Mars Science Laboratory in the sedimentary record of Gale Crater has reinvigorated the search for evidence of martian life. In this study, we used a simulated martian mudstone material, based on data from Gale Crater, that was inoculated and cultured over several months and then dried and pressed. The simulated mudstone was analysed with a range of techniques to investigate the detectability of biosignatures. Cell counting and DNA extraction showed a diverse but low biomass microbial community that was highly dispersed. Pellets were analysed with bulk Elemental Analysis – Isotope Ratio Mass Spectrometry (EA-IRMS), highresolution Laser-ablation Ionisation Mass Spectrometry (LIMS), Raman spectroscopy and Fourier Transform InfraRed (FTIR) spectroscopy, which are all techniques of relevance to current and future space missions. Bulk analytical techniques were unable to differentiate between inoculated samples and abiotic controls, despite total levels of organic carbon comparable with that of the martian surface. Raman spectroscopy, FTIR spectroscopy and LIMS, which are high sensitivity techniques that provide chemical information at high spatial resolution, retrieved presumptive biosignatures but these remained ambiguous and the sedimentary matrix presented challenges for all techniques. This suggests challenges for detecting definitive evidence for life, both in the simulated lacustrine environment via standard microbiological techniques and in the simulated mudstone via analytical techniques with relevance to robotic missions. Our study suggests that multiple co-incident highsensitivity techniques that can scan the same micrometre-scale spots are required to unambiguously detect biosignatures, but the spatial coverage of these techniques needs to be high enough not to miss individual cellular-scale structures in the matrix.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences
08 Faculty of Science > Physics Institute

UniBE Contributor:

De Koning, Coenraad Pieter; Riedo, Andreas and Wurz, Peter

Subjects:

500 Science > 520 Astronomy
500 Science > 530 Physics
600 Technology > 620 Engineering

ISSN:

2045-2322

Publisher:

Nature Publishing Group

Language:

English

Submitter:

Dora Ursula Zimmerer

Date Deposited:

22 Jul 2019 12:48

Last Modified:

22 Jul 2019 12:48

Publisher DOI:

10.1038/s41598-019-46239-z

BORIS DOI:

10.7892/boris.131956

URI:

https://boris.unibe.ch/id/eprint/131956

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