Spectral evidence for recent/ongoing activity in Mercury’s Praxiteles basin

Mercury’s surface, as revealed by the MESSENGER probe, lacks distinctive absorption features in the visible-near infrared (VIS-NIR) spectral range, except hollows which display a 630-nm feature ascribed to sulfides. The general absence of spectral features makes inference of its surface mineralogical composition challenging. The Praxiteles impact basin was inspected with newly photometrically corrected MDIS data, removing the influence of topographic shading in the spectra. We detected an absorption feature at 830 nm, spectrally compatible with Fe- or FeO-bearing minerals, that is typically associated withthe edges of bright gullies and hollows but not in fully formed hollow clusters. The morphological and spectral correlations suggest the 830 nm is linked to geologically recent, or even ongoing fresh exposure of material, as well as to the early stage of hollows’ formation. These results provide insight into the subsurface composition of Mercury and imply a crust material locally more oxidized than previously thought.