article_snippet: Most of this would have been in the northern hemisphere of Mars (illustrated).
article_snippet: However, Mars’s likely that most of how much water formed an ocean that occupied the northern hemisphere of Mars, which would have been as deep as one mile (1.6km) in places - comparable to the Mediterranean Sea on Earth.
article_snippet: ’s arid northern plains would have contained at least 12.4 million cubic miles (20 million cubic kilometres) of water.
article_snippet: But in the past, the ocean would have covered about 20 per cent of Mars’s surface area.
article_snippet: However, its’s likely that most of the water formed an ocean that occupied the northern hemisphere of Mars (illustrated) as deep as one mile in places .
article_snippet: But in the past, an ocean that occupied the northern hemisphere of Mars (illustrated) as deep as one mile in places would have covered about 20 per cent of Mars’s surface area .
article_snippet: An ancient ocean containing the lost water would have covered 19 per cent of Mars’s surface.
article_snippet: An ancient ocean containing the lost water would have had a greater volume than the Arctic Ocean, which contains 18,750,000 cubic kilometres (11.7 million cubic miles) of water.
article_snippet: By comparison, an ocean that occupied the northern hemisphere of Mars (illustrated) as deep as one mile in places covers 17 per cent of the surface of the Earth and contains more than 310 million cubic kilometres (192.6 million cubic miles).
article_snippet: An ancient ocean on Mars containing the lost water would have covered 19 per cent of Mars’s surface.
article_snippet: An ancient ocean on Mars containing the lost water would have had a greater volume than the Arctic Ocean (shown), which contains 18,750,000 cubic kilometres (11.7 million cubic miles) of water .
highlights_snippet: Most of this would have been in the northern hemisphere of Mars .
  