Description of the thesis topic

Title: Characterization of molecular (bio)signatures in planetary analogue samples: implications for habitability and space exploration

The search for traces of life and biomarkers is one of the main goals of the space exploration towards Mars and the other objects in the Solar System relevant for astrobiology (ex: ocean worlds). Terrestrial analogues have been used for decades in support of space exploration due to their similarities with the environmental conditions and mineralogies of the planetary bodies targeted by space missions. Specifically, analogues are used to guide, prepare, and optimize the flight instruments and the analytical protocols but also to help interpret the in situ data obtained by these flight instruments.
The LATMOS is involved in several national and international projects and has been participating in the development and optimization of flight instruments and their analytical protocols for years, particularly through the characterization of environments and planetary samples analogue to the planetary surfaces targeted by the current and future space mission. Numerous environments and analogues have been identified as high priority targets for astrobiology because of their extant life and diverse microbial diversity: (1) surface and deep-surface hydrothermal environments, subsurface basaltic terrains (e.g., lava tubes) and atypical aqueous environments (e.g., acid salt lakes); or for their high preservation potential in extinct life (e.g., biomarkers): (2) older terrains such as fossiliferous Precambrian strata as they can preserve records of past habitability (i.e., biosignatures). Many of these environments have been studied independently to evaluate their habitability but their (bio)geochemical processes remain poorly understood and studied on a larger scale.
The goal of this PhD is to characterize the nature, amount, and distribution of the organic molecules and biosignatures present in the analogue sample of the planetary bodies targeted such as Mars and the icy moons/ocean worlds of the gaseous giant Jupiter and Saturn (e.g., Enceladus, Europa, Titan). The samples studied will include natural samples that have been collected during various field work campaigns such as minerals from lava tubes, hydrothermal environments and fossiliferous stromatolites as well as synthetic samples (e.g., minerals-organics mixtures of interested for astrobiology) in order to highlight the geochemical processes leading to the formation of the organics detected in both the natural and extraterrestrial samples.

This overall goal of this Ph.D., in close collaboration with scientists from NASA/GSFC and the University of Georgetown (Washington D.C, USA), is to characterize the biogeochemistry of the samples using complementary analytical techniques in order to evaluate their mineralogy, microbiology, chemistry, and biosignature preservation potential. In this context, the Ph.D. student will perform analytical chemistry analyses in the laboratory, specifically extract the biosignatures from the samples using solid-liquid extractions and then analyze them using gas chromatography-mass spectrometry (GC-MS). To evaluate the capability of flight instruments to detect these biosignatures in these environments, the samples will also be analyzed using the thermal (pyrolysis) and chemical (derivatization, thermochemolysis) techniques and the analytical protocols currently used onboard martian rovers (e.g., Curiosity). Other analytical techniques may be used according to the needs, such as elemental analyses to determine the carbon content of the samples, microscopy, Raman and infrared spectroscopy, or high resolution mass spectrometry. Results will inform on the most promising samples for the search for organic (bio)signatures, and potentially life, on Mars and on the ocean worlds. They will also be used to optimize the analytical protocols for the development of future flight instrument and will allow fundamentally to characterize the links between the biological/chemical and mineralogical phases of the samples studied.

Litterature :
- Foucher, F., Hickman-Lewis, K., et al., 2021. Planetary and Space Science 197, 105162.
- Boston, P. J., et al., 2001, Cave biosignature suites: Microbes, minerals, and Mars. Astrobiology, 1(1), 25–55
- Cushing, G.E., et al., 2015. JGR Planets, 120, 1023-1043, 2015.
- Northup, D. E., et al., 2011, Lava cave microbial communities within mats and secondary mineral deposits,Astrobiology, 11(7), 601–618.
- Weng, M., Zaikova, E., Millan, M., et al., 2022. JGR Planets 127.11: e2022JE007268.
- Fishman, C., et al., 2023, Extreme Niche Partitioning and Microbial Dark Matter in a Mauna Loa Lava Tube, JGR: e2022JE007283
- Millan M. et al., Organic molecules revealed in Mars's Bagnold Dunes by Curiosity's derivatization experiment, Nature Astronomy 6 (2021)129-140.
- M. Millan et al. Sedimentary Organics in Glen Torridon, Gale Crater, Mars: Results From the SAM Instrument Suite and Supporting Laboratory Analyses, JGR: Planets, 2022, https://doi.org/10.1029/2021JE007107
- D. Bower et al., Spectroscopic Comparisons of Two Different Terrestrial Basaltic Environments: exploring potential novel biosignatures, Icarus, 2023, https://doi.org/10.1016/j.icarus.2023.115626
- S. S. Johnson, et al, Lipid biomarkers in ephemeral acid salt lake mudflat/sandflat sediments: Implications for Mars, Astrobiology, Vol. 20, N°2, 167-178, 2020, https://doi.org/10.1089/ast.2017.1812

Work Context

- This work will be conducted within the context of the ANR 'LIBIOPANE' : 'Lipid BIOmarkers in Planetary ANalog Environments' and will be linked to current and future instruments that were or are being developed at LATMOS (e.g., Curiosity, EMILI).
- The Ph.D. student will be fully integrated to the LATMOS activities in Guyancourt (main affiliation and main work location) in collaboration with the LGPM of the CentraleSupelec school. The researches will be followed very regularly by meetings with the Ph.D. advisors, as well as through weekly/bi-weekly meetings linked to the thesis subject and organized among the national and international teams. The Ph.D. committee will also be in charge of following the progress and requirements of the Ph.D. on an annual basis. The doctoral training will be ensured by the affiliated school doctorate (ED127).

Constraints and risks

- Analytical chemistry work in laboratory
- National and international travels (Europe, USA) in order to attend workshops and conferences.

Additional Information

- Master 2 student or equivalent in astronomy or planetary sciences (physics, chemistry, geology) and potentially in analytical chemistry.
- Skills and taste for experimental and instrumental work are strongly recommended as well as the capability to work within a team.
- Knowledge about methods used in analytical chemistry is a plus.