NASA finds evidence that a massive ocean once covered one-fifth of Mars’s surface (nearly half of its northern hemisphere). The size of this body of water is comparable to Earth’s Atlantic Ocean; however the Mars ocean contained more water (20 million cubic kilometers) than the Atlantic contains now.
Ultimately we can conclude this idea of an ocean covering 20% of the planet which opens the idea of habitability and the evolution of life on the planet…e now know Mars was wet for a much longer time than we thought before…Ten years ago, the story of water on Mars was an occasional flood of rocky debris every 100m years that then switched off again. We now know it’s more continuous. There were long-standing bodies of water: lakes, deltas and perhaps even seas.