Mars once had more water than we knew USA Today

There used to be more water than anyone realized on Mars, data from the Mars Reconnaissance Orbiter seems to show.
Mars’ southern highlands have considerable amounts of phyllosilicates, a type of hydrated minerals formed by extensive water exposure. However, no one knew if there were similar minerals on the northern third of the planet, because it is covered by lava plains up to a mile deep three billion years ago.
Researchers have wondered if below that layer of lava there might be hydrated minerals, indicated that eons ago liquid water flowed over the surface there as well.