Mars May Be Hiding Most Of Its "Missing" Water Underground: NASA-Funded Study Mars May Be Hiding Most Of Its "Missing" Water Underground: NASA-Funded Study The researchers from California Institute of Technology and NASA's Jet Propulsion Laboratory (JPL) found that around four billion years ago, Mars was home to enough water to have covered the whole planet in an ocean about 100 to 1,500 metres deep. Evidence found Mars' surface suggests that abundant water flowed across Mars billions of years ago Washington: Vast amounts of ancient water may have been trapped beneath the surface of Mars, according to a NASA-funded study which challenges the current theory that the Red Planet's water escaped into space.