In-situ Chemical Analysis of Lunar Regolith by Laser Ablation Ionisation Mass Spectrometry

In-situ chemical analysis of lunar regolith by laser ablation ionisation mass spectrometry. P. Keresztes Schmidt1, S. Gruchola1, A. Riedo1,2, P. Wurz1,2 and the CLPS-LIMS Team1 1 Space Research and Planetary Sciences, Physics Institute, University of Bern, Bern, Switzerland ([email protected]), 2 NCCR PlanetS, University of Bern, Switzerland. Introduction: With NASA’s increased focus on exploration of our Moon within the Artemis programme, new scientific goals have been formulated to better understand the history of our Solar System, including the evolution of the Earth-Moon system. To establish a permanent human presence on the Moon, in-situ resource utilisation (ISRU) of lunar materials is a necessity, requiring methods for in-situ analysis and selection of suitable materials. These tasks require sensitive instrumentation capable of determining the element and isotope composition of geological features found on the lunar surface. We present the current progress in developing a reflectron-type time-of-flight laser ablation ionisation mass spectrometer (RTOF-LIMS) to allow for direct, sensitive microanalysis of lunar regolith grains in-situ on the lunar surface. The LIMS system will operate in the lunar south pole region on a CLPS mission to be launched no earlier than 2028 within NASA’s Artemis programme. The CLPS-LIMS instrument: The contribution will give a general description of the instrument and the design and operations of the sample handling system. The CLPS-LIMS instrument [1-4] consists of a miniature time-of-flight mass analyser (160 mm x Ø 60 mm) to which a compact passively Q-switched Nd:YAG microchip laser operating at 532 nm (max. pulse energy of 40 µJ, nominal pulse repetition rate of 100 Hz) is coupled. The laser beam is focused onto the sample surface through the centre axis of the mass analyser by an optical system, achieving a focal spot with a diameter of about 20 μm. At the achieved laser irradiances (~ 1 GW/cm2), the sample material is ablated and ionised. Positively charged species can enter the mass analyser and arrive at the detector system according to their mass-to-charge ratio. Methodology: We will discuss the progress of experiments conducted on lunar regolith simulant material to determine its chemical and mineralogical composition on a grain-by-grain basis. The analysis is aided by machine learning (ML) methods [5] to preselect and cluster mass spectra showing distinct chemical features. Spectra of the same cluster can be e.g., co-added in order to improve the achievable limit of detection. Figure 2: Overview of the CLPS-LIMS instrument to be deployed in the lunar south pole region. Lunar regolith is ingested via the funnel and subsequently transported by a sample handling system to the mass analyser. The total height of the instrument including dust covers is ~ 26 cm. References: [1] P. Wurz et al., in 2021 IEEE Aerospace Conference (50100) (IEEE, Big Sky, MT, USA, 2021), pp. 1–15. [2] P. Wurz et al., in 2023 IEEE Aerospace Conference (IEEE, Big Sky, MT, USA, 2023), pp. 1–10. [3] P. Keresztes Schmidt et al., in 2024 IEEE Aerospace Conference (IEEE, Big Sky, MT, USA, 2024), pp. 1–10. [4] P. Keresztes Schmidt et al., in 2025 IEEE Aerospace Conference (IEEE, Big Sky, MT, USA, 2025), in press. [5] S. Gruchola et al., Planet. Sci. J. 5, 280 (2024). Figure 1: Chemical analysis of LHS-1 lunar regolith simulant by CLPS-LIMS. A pulsed laser beam is focused onto the sample surface, while the sample is continuously moving. This causes ablation and ioni s ation of the material, which is subsequently analysed by a compact RTOF-LIMS system. Select isotope concentrations are given as atomic fractions.