In this lecture, National Gallery of Art scientists discuss the ongoing adaptation of technologies used originally to identify and map minerals on Mars to better understand art in the Gallery’s collection. These new imaging techniques, based on molecular and elemental spectroscopy, have allowed researchers to develop more detailed maps of the distribution of materials such as pigments and paint binders. For example, the types of paints (oil vs. alkyd resin) used by Jackson Pollock in his famous drip painting Number 1, 1950 (Lavender Mist) were mapped. In an early Renaissance painting by Cosimo Tura, the pigments and paint binders were mapped and a preparatory sketch was revealed. In addition, these imaging technologies have been used to visualize compositions that have been painted over, such as the woman beneath Pablo Picasso’s Le Gourmet, and also to illuminate early paint composition changes in Jean-Honoré Fragonard’s Young Girl Reading.