Direct comparison of Earth, Mars, and lunar quantification accuracies derived from laser-induced breakdown spectra of rocks

Laser-induced breakdown spectroscopy (LIBS) is an established technique used for remote geochemical analysis. Recent successes on Mars rovers have made LIBS a likely technique for use on future missions to Venus, the Moon, and other airless bodies in the Solar System. To evaluate the accuracy of major element predictions in the latter environments, a large-scale database of LIBS rock spectra was collected under Earth, Mars, and vacuum conditions. Use of calibration transfer was evaluated by training models with spectra collected in one atmosphere and testing on spectra from another. A variety of metrics was used to evaluate model performance, including root mean-squared errors and the slope and y-intercept of the linear relationship between predicted and measured compositions. Prediction accuracies of major elements were similar among all atmospheres and best when conditions of training and test spectra matched. Calibration transfer facilitates respectable accuracy among spectra acquired under mismatched conditions, indicating its usefulness when difficult atmospheric conditions such as those on Venus limit the collection of calibration spectra.