Observations of the northern seasonal polar cap on Mars III: CRISM/HiRISE observations of spring sublimation

► Compositional study of the seasonal volatile layer by near-infrared spectroscopy. ► Evolution of the spectral signatures of H2O and CO2 ice during spring. ► Detailed analysis of seven different regions of interest. ► Correlation between compositional information and high-resolution imagery. ► Insights into physical processes responsible for observed sublimation activity.