Quantitative Analysis Of Tianwen-1 LIBS Spectroscopy And In-situ Resource Utilization For Martian Soil

As a widely distributed material on the surface of Mars,Martian soil is an indicator of past geological activities and climate change,and it is also the preferred choice for future human insitu resource utilization(ISRU)on Mars.Laser-induced breakdown spectroscopy(LIBS)technology has became a powerful tool for planetary in-situ detection due to its advantages of remote detection,fast detection speed,and no sample preparation.The ChemCam-LIBS on Curiosity has obtained a large amount of scientific data on the surface of Mars and has achieved a lot of research results in soil composition and geological evolution.On May 15,2021,the Tianwen-1 lander successfully landed on the surface of Mars,and the Zhurong rover successfully began to explore the Martian surface.The MarSCoDe-LIBS carried by Zhurong also obtained the scientific data from Mars,deepening human understanding of Mars.At present,the interpretation of spaceborne LIBS spectra is usually carried out by establishing a standard database by replica machine,and training quantitative analysis models on this basis.However,before the writing of this paper,due to the impact of the COVID-19,MarSCoDe terrestrial replica machine was not ready to collect standard databases,and the amount of data transmitted back by MarSCoDe-LIBS was small,and it was impossible to use machine learning,neural networks and other technical methods that require a large amount of data training to realize the sharing of quantitative analysis models of multiple spaceborne LIBS systems(ChemCam,SuperCam,MarSCoDe).In this paper,a 4-step spectral transformation approach is proposed based on the small amount of data from MarSCoDe-LIBS,the lack of applicable quantitative models and the characteristics of the spectrum itself,including:(1)intensity unit transformation;(2)wavelength recalibration;(3)interpolation;(4)energy density correction.The MarSCoDe-LIBS spectra were transformed from four aspects:intensity unit,wavelength position,channel number and instrument response,and the transformed spectra could be shared with the data and models of the target LIBS system,making it possible to use the quantitative analysis model of ChemCam-LIBS to perform multivariate quantitative analysis of the entire spectrum of MarSCoDe-LIBS.After proposing the 4-step spectral transformation approach,this paper uses the data collected by the LIBS system(SDU-LIBS)independently built by Shandong University to verify the 4-step spectral transformation approach and its combination effect with the ChemCam-LIBS quantitative analysis model,and the verification results show that the 4-step spectral transformation approach and its combination effect with ChemCam-LIBS quantitative analysis model are reliability and credibility.Then,the 4-step spectral transformation approach was combined with the ChemCam-LIBS quantitative analysis model to apply this spectral quantitative analysis method to the LIBS data from MarSCoDe-LIBS for soil detection in the landing area,and the preliminary quantitative analysis results were obtained.The quantitative analysis of the LIBS data from the soil in the Tianwen-1 landing area showed that the soil in this area are high Si content,low alkaline element content,and may be rich in magnesium and iron,and combined with other research results,it was speculated that the area had experienced many short water activities.In terms of ISRU of Martian soil,this paper takes MGS-1(Mars Global Simulant,Exolith Lab,University of Central Florida)as an example to study the feasibility of planting crops(cabbage seed as an example)in Martian soil,and the results show that Martian soil shows inhibitory effect on crop germination and growth,which mainly comes from magnesium sulfate and hematite in Martian soil.Magnesium sulfate and iron-containing minerals in Martian soil may also cause it to be unable to completely mix with water,which will also affect the growth and development of crops in Martian soil.Studies have shown that by improving irrigation conditions and the composition of Martian soil,it is completely feasible to plant and cultivate plants in Martian soil.