The search for ice in the lunar regolith is one of the goals of the selected  South Pole Seismic Station experiment onboard the deployed payload of Artemis4. This is also the goal of the seismic experiment onboard ChangE'7 and of the ongoing LGPR project merging rotaphones and GPR proposed by IPGP, ISAE for seismic and LATMOS for GPR. In order to prepare better the scientific analysis of CE'7 LS data and the implementation of those experiment targeted for launch in 2028-30,  it is mandatory to develop the end-to-end SPSS and LGPR instrument methodology and to improve our knowledge of the impact of ice deposition on the regolith seismic velocities. These are the two main goals of the PhD project.

Regolith is characterized by very low seismic velocities and very high porosity. The first goal of the PhD will be to model the seismic rotation effects that both SPSS and a rover might encounter on the Moon and to calibrate the transfer function in rotation and translation of SPSS or a rover, as a function of the regolith properties and of the position and performances of the geophones mounted on the structure. We will start with the methodology used for InSight leveling system [1]  and will re-process the 6 axis Martian SEIS data to extract rotation effects measured during the HP3 penetration tests. We will then develop the specificities for the Moon, for either SPSS or LGPR and for either near-field or far-field sources, integrating here the lessons from the analysis of the Apollo geophones data of Apollo 17. On SPSS, three geophones are baselined, enabling a reconstruction of Rayleigh wave rotation, while on the rover projects, six are planned, for a full 6 axis rotation/translation reconstruction. In addition and for SPSS, the first of the active seismic source activations will be made in near-field with respect to seismic wave propagation. We will therefore study and model  the transition from near-field to far-field on rotation effects. 

The final product will be the complete transfer function between the subsurface shear wave velocity depth profile and the recorded data. This will request tests in laboratory with mockup of SPSS and rovers, for determination of  the transfer functions and tests on pergelisols, to be made in collaboration with Polytech. Montreal, ISAE and LATMOS, for determination of the seismic subsurface profile.

The second goal of the thesis aims to characterize the variation of the shear velocity as a function of ice content, when the ice deposition is made through condensation of water vapor.  Ice  on the Moon has indeed not been deposited through the cooling of liquid vapor, but most likely through the accumulation in the regolith porosity of vapor phase water in colds traps. Many experiments have demonstrated that very small fraction of ice in the regolith can double the shear wave velocity [3]. These experiments are however all generating the regolith-ice mixture by freezing wet regolith and therefore with the liquid-solid transition of ice, which is likely not the process of ice deposition on the Moon. 

In collaboration with ENPC and Polytech Montreal, we will design and realize an artificial cold trap in which we will generate such accumulation of vapor phase water. This will use the existing  Planetary Environment chambers in IPGP and vacuum  facilities, and will be able to simulate  cold traps down to liquid nitrogen temperature (~80 K). We will integrate in this artificial cold acoustic measurements of the shear velocities, in ways similar to what was done for InSight [2] and,  possibly, of the electromagnetic permitivity, to fully characterize the impact of ice on seismic velocities and prepare future interpretation of Joint seismic-GPR experiments.  We expect the results of this goals to be also used in the interpretation of the seismic cutoff of impacts detected by the ChangE'7 Lunar Seismograph experiment and of the Lunar Environmental Monitoring Station (LEMS), which South Pole landing and operation on the Moon (summer 2026_for LS, early 2028 for LEMS) will likely occur before the end of the PhD (in fall 2029). The two stations will indeed land in the South Pole and will be surrounded with about 30% of areas in cold traps, and we expect therefore the same fraction of detected impacts to occur in cold-trap, with therefore higher cutoff frequencies [4]. 

The last goal of the PhD will be to contribute to the analysis of field tests aiming to demonstrate the complementarity between the seismic-rotation measurements and the Ground Penetrating measurements, in collaboration with LATMOS. 

References:  [1] Fayon,..,Lognonné et al., Space Science Review, 214:119, doi:10.1007/s11214-018-0555-9, 2018. [2] Delage, P., ...., Lognonné P.,  et al. , Space Sci Rev, 211:191, doi: 10.1007/s11214-017-0398-9, 2017. [3] Tsuji ..., Kawamura, 

Icarus, 404:115666, doi: 10.1016/j.icarus.2023.115666, 2023 [4] Froment,  Lognonné et al., Geophys. J. Int., 238:156, doi: 10.1093/gji/ggae144, 2023.

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For more Information about the topics and the co-financial partner (found by the lab!); contact Directeur de thèse - lognonne@ipgp.fr

Then, prepare a resume, a recent transcript and a reference letter from your M2 supervisor/ engineering school director and you will be ready to apply online before March 13th, 2026 Midnight Paris time!