Analysis at submillimeter scale, or microanalysis, is the next step forward for in situ planetary exploration. On the Moon, returned samples enabled the identification of major crustal components however a diversity of smaller distinct exposures including polar regions with hydrated minerals or ice have been observed only from orbit and their origin is poorly understood. Associating chemical composition with submillimeter textures at or near the mineral grain scale can unambiguously identify and classify these new types of lunar rocks and regolith, providing evidence on the history of environments leading to their formation. Such in situ microanalyses are also crucial for future missions to sort and select among samples those worthy of return to Earth.
Laser Induced Breakdown Spectroscopy (LIBS) is a technique that uniquely provides elemental abundance at submillimeter scale on naturally exposed rocks while removing surface dust. It can quantify the abundance of major elements (Si, Fe, Mg, Al, Ca, K, Na, Ti) in addition to volatiles (C, H, N, O, P, S) as well as other light and/or minor elements (Li, Sr, Cr, Rb, Mn…). Uniquely resolving hydrogen and deuterium separated by 0.2 nm, LIBS analyses under vacuum even have the potential to estimate D/H on lunar ices using the right optics and detector, a key measurement in understanding the history of water reservoirs on the Moon.
LIBS is now widely used in the laboratory for microanalyses, and on Mars a decade of experience with the ChemCam instrument, and now SuperCam (led by IRAP in France) and MarsCoDe (on China’s Zhurong rover), has proven the technique’s reliability and capability to analyze rocks at a submillimeter scale for geological investigations. Its feasibility in the vacuum of the lunar surface has also been proven. Now a set of small handheld commercial devices ≤ 2 kg are available for geochemical analyses. In addition, a 1.1 kg LIBS instrument has been developed to TRL-8 for the Chandaryaan 2 and 3 mission. Based on heritage, IRAP and CNES are now developing µLIBS, a new 1.5 kg instrument to perform LIBS on the Moon or Mars with a miniaturized architecture.
µLIBS will operate at a distance of 20 to 50 cm and will include a 2-axis actuated scanning mirror to point to diverse targets in a workspace below the platform. This mechanism will enable precise pointing of the < 100 µm focused laser spot to perform closely-spaced grids mapping areas < 1 cm². An embedded remote micro-imager provides dust-free micro-textures with elemental map overlaid. The µLIBS laser operates faster than its predecessors, making up to 30×30 micro-scale maps under 1 hour to detect minor phases down to 0.1% and map their distribution. It can provide micro-scale elemental analyses with a science return similar to contact instruments, for lower cost, operating remotely with high-precision from a mobile platform with no need of arm deployment nor platform turret.
The main objective of the proposed thesis is to explore the capabilities of the µLIBS instrument in its adaptation to future lunar missions. As part of CNES phase A development, a functional µLIBS prototype is currently developed and will be assembled by the end of 2024. After engineering development, the platform can be used for laboratory tests of future µLIBS measurements to demonstrate its capabilities in addressing questions related to lunar exploration:
Quantification of major and minor elements to identify lunar basalts and other expected or hypothesized crustal components.
Detection and quantification of hydrogen-bearing phases and minerals to characterize the hydration of a rocky sample under vacuum.
Characterization of the effect of distance and laser focus reflecting expected operating conditions on the Moon to determine the uncertainty and robustness of µLIBS measurements.
These tests can be performed on existing collections of rock samples at IRAP and partner laboratories, and may require specific sample preparations and analyses. The proposed work involves:
Adaptation of the µLIBS development prototype into a laboratory setup for instrument calibration and dedicated scientific testing.
Development of data processing routines for LIBS data and models for calibration and quantification of major and minor elements.
Contribution to instrument design discussions within the µLIBS team for future integration on lunar exploration missions (Artemis, CLPS, and other international opportunities)
For more Information about the topics and the co-financial partner (found by the lab !):
Directeur de thèse – william.rapin@irap.omp.eu
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 15th, 2024 Midnight Paris time !