It was already known that liquid water can exist on about half of Mars, though in a very narrow temperature range (around 0C). The green and blue bits have the

It was already known that liquid water can exist on about half of Mars, though in a very narrow temperature range (around 0C). The green and blue bits have the adequate pressures for liquid water to exist: https://upload.wikimedia.org/wikipedia/commons/2/2c/Mars_topography_%28MOLA_dataset%29_with_poles_HiRes.jpg https://upload.wikimedia.org/wikipedia/commons/2/2c/Mars_top... Very narrow phase-space in which liquid water can exist, the yellow rectangle is conditions on Mars: https://i.imgur.com/BeDg1KM.gif https://i.imgur.com/BeDg1KM.gif