Design, Function, and Implementation of China's First LIBS Instrument (MarSCoDe) on the Zhurong Mars Rover

Abstract

MarSCoDe (Mars Surface Composition Detector) is China's first instrument for Mars material analysis, which accompanies the Zhurong Mars rover landing on Utopia Planitia and will detect interested Martian rock and soil targets based on laser-induced breakdown spectroscopy (LIBS) technique. MarSCoDe consists of a bioxial pointing mirror (BPM), an optical head, a calibration targets assembly (CTA), a spectrometer module (SM) and a payload controller. The MarSCoDe is scheduled to analyze twelve major elements. To achieve accurate quantitative analysis and classification of Mars targets, a PSO (particle swarm optimization)-based calibration scheme is adopted to correct the spectral shift due to the temperature change on Mars, and then a convolutional neural network (CNN) was proposed to implement the analysis of elements. Finally, the mineral types of Martian objects will be identified according to the alkali silica ratio. The detection results of the MarSCoDe will provide further information about the evolution of Mars. In planetary exploration, laser-induced breakdown spectroscopy (LIBS) is an appealing element detection technology due to its special capabilities, such as dust removal, in situ analysis, and analysis of light elements (atomic mass <20). With the successful landing in 2021 of NASA's Perseverance rover and CNSA’s Zhurong rover, plus NASA's Curiosity rover in 2012, there are now three LIBS payloads working on Mars. The Zhurong rover landing on Utopia Planitia on May 15, 2021, contains China's first LIBS instrument, the MarSCoDe (Mars Surface Composition Detector). Its purpose is to detect the atomic spectra of representative rock and soil targets in the Utopia Planitia area and to analyze the material composition of the Martian surface. The detection results of the MarSCoDe will provide further information about the evolution of Mars. The Zhurong Mars rover consists of a navigation and terrain camera, a multispectral camera, a magnetic field detector, a climate detector, a subsurface detection radar, and the LIBS instrument, MarSCoDe, shown in Fig. 1. The MarSCoDe (marked in blue in Fig. 1) consists of five parts: a bioxial pointing mirror (BPM), an optical head (Fig. S1), and a calibration targets assembly (CTA), which are outside the rover’s cabin, and a spectrometer module (SM) and a payload controller, which are inside the cabin. Pulsed laser is emitted and focused via the optical head, which is reflected onto the BPM to detect rocks. The excited LIBS signals from the rocks are collected through the optical head