Geochemistry by Laser-Induced Breakdown Spectroscopy on the Moon: Accuracy, Detection Limits, and Realistic Constraints on Interpretations

Abstract

After its successful implementation on the surface of Mars, laser-induced breakdown spectroscopy (LIBS) is likely to be employed on a diverse array of other solid bodies in our Solar System. Here we address the accuracy and quantification limits of LIBS under the vacuum conditions found on the Moon relative to what is known about its geochemistry. The interplay among accuracy as represented by root mean-squared errors (RMSE), the median concentration, and quantification limits (LOQ) of LIBS analyses for each of 69 elements is evaluated. This comparison shows that several key elements in lunar geochemistry cannot be well-studied with LIBS, including K₂O, S, Rb, Br, and C. Conversely, highly accurate analyses of SiO₂, CaO, and many minor and trace elements such as Mn, Yb, and Zn are possible under conditions found on the Moon. Use of LIBS must always be considered in the context of the geochemistry and geology of the target materials.