The ESA-Roscosmos ExoMars Trace Gas Orbiter has spotted significant amounts of water at the heart of Mars’ dramatic canyon system, Valles Marineris.
The water, which is hidden beneath Mars’ surface, was found by the Trace Gas Orbiter (TGO)’s FREND instrument, which is mapping the hydrogen – a measure of water content – in the uppermost metre of Mars’ soil.
While water is known to exist on Mars, most is found in the planet’s cold polar regions as ice. Water ice is not found exposed at the surface near the equator, as temperatures here are not cold enough for exposed water ice to be stable.
https://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration/Exploration/ExoMars/ExoMars_discovers_hidden_water_in_Mars_Grand_Canyon