Image Credit: Vadim Sadovski/Shutterstock.com Laser-induced breakdown spectroscopy (LIBS) instruments built into the latest generation of Martian rovers will provide planetary scientists with a wealth of new data on Martian geology – but to learn from it, they will need to overcome a critical challenge with their machine learning models. Because scientists do not have real Martian rock samples to work with in the lab, there is no training data to calibrate the machine learning models usually used to analyze LIBS spectra. Though scientists have improvised make-shift training sets using Earth rocks, results are still skewed by ‘physical matrix effects’.