High Resolution Map of Water in the Martian Regolith Observed by FREND Neutron Telescope Onboard ExoMars TGO

Studies of water content in the Martian subsurface by means of neutron spectroscopy is a well-known technique, very sensitive to water abundance. The FREND instrument onboard the ExoMars TGO is the latest experiment of that kind. Its major characteristic and advantage compared to the predecessors is its capability of high spatial resolution measurements - massive collimator shields FREND's detectors, allowing for a narrow field of view. In this study we present a global map of Water Equivalent Hydrogen (WEH) in the upper meter of the Martian subsurface, which is built based on the FREND data. We show that it contains more local features and reveals more structure than analogous maps from omnidirectional experiments, available previously. Further analysis shows that local water-rich regions can be located through the analysis of the FREND data, some of these containing about 20 wt% of WEH - a very unusual amount for regions at moderate latitudes, where free water and water ice are thought to be unstable in the shallow subsurface.