Most of humanity’s Mars-bound fleet of spacecraft is searching the Red Planet for evidence of its watery past. New evidence gathered by ESA’s Mars Express spacecraft is helping scientists fine tune their theories. A radar instrument on the spacecraft has turned up water ice in Mars‘ upper layers; a mineral mapping instrument has discovered chemicals formed in a wet environment; and its powerful camera has picked out obvious features on the surface of Mars formed by running water. Here’s a breakdown of what Mars Express has found so far:
https://www.esa.int/Science_Exploration/Space_Science/Mars_Express/Mars_Express_and_the_story_of_water_on_Mars