Reference : UMR5274-VALDEL1-018
Workplace : GRENOBLE
Date of publication : Tuesday, May 3, 2022
Scientific Responsible name : Olivier POCH
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 September 2022
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
Determining the composition of Ganymede's surface and its chemical evolution: Spectroscopic measurements of analogues and experimental simulations
Ganymede, the largest satellite of Jupiter, has an inner ocean and a dichotomous surface with light terrains, dominated by ice and probably salts, and dark terrains whose composition is very poorly known. Determining the composition of Ganymede's surface is a major objective, as it provides insights into the internal composition, thanks to materials excavated by impact or under the effect of tectonics. Ganymede has an exosphere that is generated by surface sputtering, triggered by magnetospheric particles irradiation, and by the bombardment of cometary and interstellar dust.
The observation of Ganymede by the JWST space telescope during the summer of 2022 will provide unprecedented surface spectra in the mid-infrared range, (2.9-11.7 µm), which should bring valuable constraints in terms of composition and nature of the physico-chemical processes involved. The interpretation of these spectra requires the conduct of laboratory experiments, which are the subject of this thesis. In a first part, the optical properties of model materials will be studied in cryogenic conditions using spectro-gonio-radiometric devices (bidirectional reflectance, phase function), and transmission measurements (optical constants). In a second part, the effects of magnetospheric particles will be studied by electron and ion irradiation experiments, to produce reference spectra of irradiated materials, as well as fundamental physical parameters essential to exospheric models. This thesis work is funded by the ANR (“Agence Nationale de la Recherche”) via the project PRESSE (PREparing Jupiter's System Exploration with JWST), in the frame of national (LESIA, LATMOS, LMD laboratories) and international collaborations (Early Release Science program ERS 1373/JWST).
IPAG laboratory is a Joint Research Unit of 150 people under the supervision of the CNRS and the University of Grenoble Alpes.
The doctoral student will be supervised at IPAG by Eric Quirico, professor at the University of Grenoble Alpes, and Olivier Poch, researcher at the CNRS. The thesis will be conducted within the framework of the ANR PRESSE (PREparing Jupiter's System Exploration with JWST) and the JWST Early Release Science observation program (ERS 1373, Observations of the Jovian System as a Demonstration of JWST's Capabilities for Solar System Science), which will involve regular interactions and meetings with LESIA (T. Fouchet, D. Bockelée-Morvan, E. Lellouch), LATMOS (F. Leblanc) and LMD (S. Guerlet), and with all of the international team of ERS 1373.
The doctoral student will benefit from external views and critical advice at IPAG during presentations of his/her work at meetings of the thematic group "Spectroscopy and chemistry of small bodies and cosmo-materials" and at meetings of the Spectre and Planeto teams, which take place every week on average. The doctoral student will present his work to the entire laboratory each year during the IPAG Thesis Day, and possibly during a seminar if the opportunity arises. A thesis committee will provide an outside perspective on the progress of the thesis and its supervision. The doctoral student will benefit from the support of the IPAG doctoral support group to ensure that the thesis takes place in good conditions.
IPAG, the project will benefit from the necessary experimental infrastructure and associated funding (ANR PRESSE, CNES, Europlanet 2024). Experiments at GANIL and on the SIRIUS accelerator are carried out on the basis of calls for projects. The supervisors have several years of experience in ion irradiation at GANIL and recurring relationships with the host team. The financial environment will allow the promotion of work in international conferences.
Promotion of results will be done throughout the thesis by communication during conferences, seminars, workshops, and publications in peer-reviewed journals. Two publications, one on each of the aspects of the project, are possible during this thesis.
The planned collaborations will take place within ANR PRESSE and the ERS/JWST consortium, with the host team at GANIL and with the University of Bern. The ERS/JWST team is international.
Constraints and risks
The doctoral student will be trained in good practices for working safely in the laboratory, via his supervisors and prevention assistants.
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