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PhD M/F: evolution of organic matter in the environment of Mars

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Français - Anglais

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General information

Reference : UMR7590-LAUREM-004
Workplace : PARIS 05
Date of publication : Thursday, June 25, 2020
Scientific Responsible name : Sylvain Bernard et Laurent Remusat
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 October 2020
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly

Description of the thesis topic

Experimental fossilization under Martian conditions

Description

Conditions on Mars were probably favourable for life 4 billion years ago, when life started to exist on Earth. This is why NASA and ESA are sending rovers to Mars (this year and in 2022) to search for (organic) traces of life. The (sub)surface of Mars is seen as a giant freezer that has potentially preserved traces of life for billions of years. However, most Martian sediments have been subjected to episodes of fluid circulation, as shown by the presence of multiple veins, which are detrimental to the preservation of organic molecules.

Determining the origin (biogenic or abiotic) of the organic compounds trapped in ancient Martian sediments requires experimentally documenting the evolution of organics during a geological history involving fluid circulation events. This is the philosophy of this PhD.

This thesis work will be mostly based on laboratory experiments. The student will perform fossilization experiments under Martian conditions using clay minerals emblematic of Mars in which a highly reactive fluid rich in sulphates will circulate. The experiments will be conducted under CO2 at different temperatures for different durations in closed and open systems. The gaseous, liquid and solid fractions of all the experimental residues will be characterized at multiple scales using recent microscopy and spectroscopy tools.

The results of this PhD work will help determine what to look for on Mars: by providing robust experimental constraints on the impact of ageing and weathering processes on organic materials, this PhD work will greatly simplify the search for ancient biosignatures on Mars. In addition, the results will provide a strong rationale for the search for potential traces of life on other planetary bodies, including rocky and/or icy bodies (such as Ceres, Enceladus or Europa) on which organic carbon and/or clay minerals have been detected.

Keywords: Mars, Biosignatures, Experimental Fossilization, Organic Molecules, Clay Minerals

Profile required: Carrying out this subject requires a pronounced taste for experimentation and mineralogy characterization tools.

Work Context

The thesis will take place at the Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, a joint research unit between the Centre National de la Recherche Scientifique (CNRS), Sorbonne University and the Muséum National d'Histoire Naturelle in Paris. The IMPMC is a multidisciplinary institute of physics, earth sciences and biophysics and bioinformatics. IMPMC's research strategy is based on ambitious projects in condensed matter physics, Earth sciences in the broadest sense and biology, the three fundamental components of the unit.
The thesis will be carried out within the ROCKS team, one of whose research axes aims to improve understanding of the processes that control the evolution of organic molecules in rocks during geological processes.

The attached doctoral school is ED 227 "SCIENCE DE LA NATURE ET DE L'HOMME : ÉCOLOGIE ET ÉVOLUTION" of the MNHN, specializing in Geochemistry - Cosmochemistry.

Thesis supervisors: Laurent Remusat and Sylvain Bernard (CR CNRS - ROCKS team).

Constraints and risks

The major part of the thesis will take place at the IMPMC, on the Buffon sites at the National Museum of Natural History and Jussieu at Sorbonne University.

This thesis has a very strong experimental component. The experiments and the characterization of the samples will be carried out at the IMPMC.

A few trips in France and abroad are to be expected, in order to collaborate with remote teams for the use of instrumentation not available at the IMPMC.

Several trips abroad are also possible, notably to present the progress of the work at international conferences.

This thesis will require handling chemicals and conducting experiments under high pressure. The laboratory has the necessary safety equipment and it will be made available to the recruited person.

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