Description du sujet de thèse

To learn more about the fascinating new worlds of exoplanets, several space telescopes have been designed, such as the JWST (James Webb Space Telescope, launch in 2021) and Ariel (Atmospheric Remote-sensing Infrared Exoplanet Large Survey, launch in 2030). The broad wavelength coverage and high-sensitivity of the instruments on-board these telescopes will allow us to extract much more information from their data than what has been possible so far, leading to numerous breakthroughs. However, retrieval of exoplanets atmospheric composition heavily relies on molecular spectroscopy which quantifies the abundances of various molecular species, revealing the composition and physical conditions of these distant worlds. High resolution spectroscopic data are essential for the interpretation of exoplanetary spectra observed by the telescopes. However, the lack of IR laboratory data for many molecules that are potential bio-signatures candidates or their precursors, severely limits exoplanet modelling. In particular, the absence of complete high-resolution IR spectroscopic data for methyl-containing molecules exhibiting Large Amplitude Motions (LAMs) highlights the need for significant improvements in this field. At LISA we have experts in modelling LAM's. Significant improvements in the theoretical modelling are required for a number of internal rotors in order to generate reliable molecular parameters and enabling accurate predictions of line frequencies and intensities for the (exo)planetology community. Within the ANR project “EXOBIOLAM (TOWARDS THE DETECTION OF EXOPLANET BIOSIGNATURES WITH LARGE AMPLITUDE MOTIONS USING HIGH RESOLUTION SPECTROSCOPY)”, the hired PhD candidate will contribute to develop a comprehensive Hamiltonian model and to analyze the microwave and infrared spectra for different potential biosignature molecules containing one or two –CH3 internal rotor(s). The PhD student will also participate to the recording and gathering of new measurements in the spectral range mentioned above. She/he will be involved in the application of these newly spectroscopic parameters to the study of exoplanetary atmosphere by integrating these new high-resolution spectroscopic data into an innovative model coupling kinetic models and retrieval for exoplanets. At LISA, one member of our consortium and her collaborators are the only ones at the international level to develop chemical schemes validated on experimental data under very varied pressure and temperature conditions, reflecting the diversity of exoplanets.

Objective: The first objective of the PhD is to develop the theoretical models and tools to analyze the microwave, (sub)millimeter, THz and infrared laboratory data for different molecules exhibiting one or two internal rotor(s) and prepare line-by-line predictions for the explanetology community. The PhD student will also participate to the recording and gathering of new measurements in the spectral range mentioned above. The second objective is the application of the newly developed spectroscopic data in the study of planetary atmospheres, using an innovative model coupling kinetic models and retrieval for exoplanets. This work will be performed at LISA with experts in LAM's spectroscopy and in modeling of (exo)planetary atmospheres.

The PhD student will be co-supervised by Isabelle Kleiner and Olivia Venot at LISA as well as with Dr P. Asselin from the laboratory « De la Molécule aux Nano-objets : Réactivité, Interactions et Spectroscopies » (MONARIS, Paris). The theoretical development and fitting of the spectroscopy data will be performed in close collaboration with the partners of the ANR EXOBIOLAM, at the MONARIS laboratory and at the French SOLEIL Synchrotron for the new measurements in infrared range, with the laboratory LPCA (« Laboratoire de Physico-Chimie de l'Atmosphère » (LPCA, Dunkerque) for the THz range, and with the « Laboratoire de physique des lasers, atomes et molécules» (PhLAM) laboratory in Lille for quantum chemical calculations to model anharmonic interactions. The radiative transfer model for transit spectroscopy has been used by members of our ANR consortium (O. Venot, LISA) in collaboration with Drs. P. Drossart and J.-P. Baulieu from the Institut d'Astrophysique de Paris (IAP) and with Dr. P. Lavvas from the “Groupe de Spectrométrie Moléculaire et Atmosphérique” (GMSA, Reims). National and international collaborations will also take place.

Contexte de travail

The PhD program takes place within the ANR project “EXOBIOLAM” led by Dr Isabelle Kleiner.
The Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA) is a Joint Research Unit of the CNRS, the Université Paris-Est Créteil, and the Université Paris Cité. It belongs to the Observatoire Des Sciences de l'Univers EFLUVE and to the Research Federation IPSL. It is located in Créteil, an important student city in the Paris region. The research lab is a leader in atmospheric modeling at the international level. Its main mission is to contribute to improving our knowledge of the functioning of the Earth's and planetary atmospheres in order to understand their past evolution and predict their future trajectories. The PhD candidate will join the SPECAT spectroscopy group, whose main objectives are the developments of laboratory theoretical and experimental spectroscopy on molecules with astrophysical or atmospheric and planetological applications. They are internationally recognized as world class experts in molecular spectroscopy from both a modeling and experimental point of view. They are strongly involved in several international databases for molecular spectroscopy such as HITRAN, GEISA, etc. The thesis will be co-directed by Dr. O. Venot from the Exobiology and Astrochemistry group, whose main objectives are the search for molecular structures and the study of the various physico-chemical processes governing the chemical evolution of various astrophysical objects (exoplanets, comets, Mars, Titan…). They are strongly involved in the analysis of observational data from ground-based facilities and space missions.
The PhD student will also participate to experimental work at the laboratory « De la Molécule aux Nano-objets : Réactivité, Interactions et Spectroscopies » (MONARIS, Paris) under the direction of Dr. P. Asselin.

Contraintes et risques

Short trips abroad