Fig. 1: Global distribution of near-surface hydrogen.

a–c Pixon reconstructed Mars Odyssey Neutron Spectrometer water equivalent hydrogen (WEH) data by Wilson et al., 2018 overlaid onto Mars Orbiter Laser Altimeter (MOLA) shaded relief map (illumination from the northeast)141. a Dotted boxes mark the locations of inset (b and c). b Excess hydrogen around Meridiani Planum and Syrtis Major. c Excess hydrogen around the Medusae Fossae Formation (MFF) and Apollinaris Mons.