Mars also has water in the form of hydrated minerals — that is, minerals that have water chemically bound to them. Future crewed missions to Mars could extract this water by heating the hydrated minerals.
Some liquid water may occur transiently on the Martian surface today but is limited to traces of dissolved moisture from the atmosphere and thin films, which are challenging environments for known life. Vincent Chevrier, a planetary scientist at the University of Arkansas said, “Only some very specific brines (calcium or magnesium perchlorates for example) would be stable enough to survive for several hours per day on Mars and only in specific regions.” He said, “We don’t have any evidence for it, but could have adapted to these extreme environments.”
He added, “The presence of water ice is enough since it can be simply melted by humans to provide liquid water during their stay on the planet.” Stephen Kane, a planetary scientist at the University of California said, “This result makes me wonder if Mars had a smaller initial water inventory than previously suggested.”