LIBS for planetary in-situ exploration: an overview of research activities at DLR

Kurzfassung

Laser-induced breakdown spectroscopy (LIBS) is an atomic emission spectroscopy technique from which the elemental composition of a target can be derived qualitatively and quantitatively. With a pulsed high energy laser, material from the sample surface is ablated which evolves into a small plasma of excited atoms, ions and simple molecules. Spectral analysis of the emitted plasma radiation gives spectra with multiple characteristic elemental and occasionally also molecular emission lines that correspond to the composition of the sample. The LIBS technique has several advantages for the geochemical analysis of extraterrestrial surfaces: It is fast, needs only optical access to the target and is sensitive to all elements including hydrogen [1]. The first extraterrestrial LIBS instrument is ChemCam which is onboard NASA’s Mars Science Laboratory (MSL) and has been successfully measuring the geochemical composition of rocks and soils in Gale crater, Mars since 2012 [2]. Further extraterrestrial LIBS instruments are ChemCams follow-up instrument SuperCam on NASA’s Mars 2020 mission [3,4], the MarsCoDe instrument on CNSA’s Tianwen mission [5] as well as a LIBS instrument as part of the ISRO Chandrayaan-3 mission to the Moon [6].

The German Aerospace Center (DLR) in Berlin has long expertise in LIBS research for applications in planetary exploration. A focus of its activities is on providing a better understanding of the extraterrestrial laser-induced plasmas in order to help in the analysis and interpretation of real mission data. The research at DLR builds on several approaches: High performance and in parts very unique laboratory set-ups can be used to do feasibility studies and fundamental research on LIBS in specific extraterrestrial ambient conditions [7-12]. At the same time, we design, develop and work with compact instrumentation to demonstrate the capabilities of potential LIBS payloads, to simulate the performance and to prepare the development of space instruments which are limited in mass, size and power consumption. Prototype hardware is tested in the laboratories [13-15] and integrated into DLR planetary exploration robots and tested in the field [16]. Instrumental and methodological developments are complemented by investigating novel approaches to analyze the data including modelling and machine learning [17,18]. Furthermore, we are involved via Co-I ships in the operations and science of the ChemCam and SuperCam instruments.

The objectives of our LIBS activities can be summarized as the informed development of LIBS instrumentation for space exploration and the investigation of advanced data analysis strategies for LIBS data from space missions in order to maximize the scientific return. Here we want to report on the most recent findings and give an outlook on future planned activities