火星车载激光诱导击穿光谱仪(MarsCoDe)在轨定标样品选取研究

我国首次火星全球遥感与区域巡视探测任务已获批立项，首个火星探测器也即将前往火星。为满足火星物质成分分析的需求，我国研制了不同类型的火星物质成分分析仪器，其中包括火星表面成分探测仪（MarsCoDe），应用了激光诱导击穿光谱技术（laser-induced breakdown spectroscopy，LIBS）。火星表面覆盖尘埃，探测仪器想要准确获取火星尘埃之下的物质成分，必须剥去尘埃或者进行破坏从而深入岩层取样。LIBS可以用激光烧蚀待测物体表面，获得深部物质光谱信息，在火星表面探测中具有其他仪器无法取代的优势。LIBS在火星探测中几乎适用于探测每一个元素，包括轻元素H，Li，Be，B，C，N，O等，帮助寻找有机物和含水地质过程的证据。由于LIBS在火星环境工作，等离子体的物理性质与地球上完全不同。为了确保火星车载LIBS返回数据的光谱质量，需要对LIBS在着陆后开展在轨定标。借助火星车的携带在轨定标样品，对探测数据进行在轨定标，确保返回数据的可靠性。定标样品的选择是一项十分重要的工作，存在仪器工程条件限制、定标样品类型的代表性、元素成分分布范围、样品稳定性等多种考虑因素，需满足科学任务的同时达到加工工艺要求。总结了国外已有的火星车载LIBS在轨定标的研究进展，重点分析了LIBS在轨定标样品选择依据、国外选择样品的优缺点，并总结经验提出了几点建议，为我国在轨定标工作提供参考。对火星探测数据的正确解译，对未来研究火星的起源、火星的长期地质演变过程等具有重要的科学意义。

Researchon the Selection of Mars Onboard Laser Induced Breakdown Spectrometer (MarsCoDe) Calibration Samples

The first Mars Global remote sensing and regional survey mission of China has been approved for the first time, and the first Mars probe is going to Mars. In order to meet the needs of Mars material composition analysis, different types of instruments on Mars rover have been developed in China, including Mars Surface composition detection Package (MarsCoDe) using laser-induced breakdown spectroscopy (LIBS) technology. Because the surface of Mars is covered with dust, we must get rid of the dust layer or destroy rock surface if we want to detect the material composition under the Mars dust accurately. LIBS can be used to ablate the surface of the object by its laser, and obtain the spectral information of deep rock. In addition, LIBS is almost suitable for detecting every element in Mars exploration, including light elements H, Li, Be, B, C, N, O, etc., which helps to find evidence for organic matter and water-bearing geological process. Due to Mars environment, the physical properties of the plasma are completely different from those on earth. In order to ensure the quality of the returned LIBS spectral data, it is necessary to carry out onboard calibration after landing, meanwhile carrying calibration board with specific standard samples on Mars rover, for data correction, ensuring the reliability of the returned data and more accurately interpreting the Martian surface material. The selection of calibration samples is a very important work. There are various factors such as the limitation of equipment engineering conditions, the representativeness of the calibration sample types, the distribution range of the elements and the stability of the samples. In this paper, we summarized the research progress of onboard calibration of Mars onboard LIBS and focused on analyzing the selection criteria of LIBS calibration samples and the advantages and disadvantages of foreign sample selection. After summarizing experiences, some suggestions were put forward to provide reference for our onboard calibration work. This article is of scientific significance to the correct interpretation of Mars exploration data and future research on the origin of Mars and the long-term geological evolution of Mars.