If Mars Had Water, Where Did It Go?
Some of it was lost to space (Mars doesn’t have a magnetic field to protect it from solar wind), some of the water reacted with volcanic rocks and then got trapped in minerals, and some of the water is still there today, frozen into the ice caps and in permafrost layers below the ground. Professor, Astronomy, Vanderbilt University, and the author of ‘Life on Mars,’ from which the below is drawn
If we take all the water on a planet, put it on the surface of the planet, and spread it out evenly over 100% of the surface area, we would have what planetary scientists call a ‘global ocean.’ However, if, in addition to the evidence from atmospheric gasses, we use the visual evidence for flowing water on the surface of Mars, which is clear in the form of dried up river valleys and outflow channels that scar the ancient surface of the red planet, we can estimate that Mars once had enough water to generate a global ocean with a depth of 1,500 to 3,000 feet.
Source: gizmodo.com