article_snippet: , we know Mars once had water - but until now we didn't know how much.
article_snippet: Scientists have provided the best estimates yet, claiming it once had more water than the Arctic Ocean - and Mars kept these oceans for more than 1.5 billion years.
article_snippet: The findings suggest there was ample time and water for life on Mars to thrive, but  over the last 3.7 billion years Mars has lost 87 per cent of Mars water - leaving Mars barren and dry.
article_snippet: Nasa scientists in Maryland have calculated how much water was once on Mars.
article_snippet: The study by scientists at Nasa’s Goddard Space Flight Center in Greenbelt, Maryland, is the first to determine just how much Mars Mars had in Mars past.
article_snippet: During Mars wet Noachian period - 4.1 to 3.7 billion years ago - Mars is estimated that Mars had enough water to cover the entire surface in a liquid layer 450 feet (137 metres) deep.
article_snippet: Published in the journal Science, the research estimates that, in total, what is now Mars
article_snippet: ‘Our study provides a solid estimate of how much water Mars once had, by determining how much water was lost to space,’ said Dr Geronimo Villanueva, first author of the paper and a scientist at Nasa’s Goddard Space Flight Center.
article_snippet: With this work, we can better understand the history of water on Mars.
article_snippet: The most interesting conclusion, though, is that Mars stayed wet for longer than previously thought, which means it was habitable for longer.
article_snippet: We now know that Mars was wet for a much longer time than We thought before,’ said Dr Michael Mumma, co-author of the study and Senior Scientist at Nasa Goddard.
article_snippet: Curiosity shows it was wet for 1.5 billion years, already much longer than the period of time needed for life to develop on Earth.
article_snippet: And now we see that Mars must have been wet for a period even longer.
article_snippet: During its wet Noachian period, 4.1 to 3.7 billion years ago, its is estimated that Mars had enough water to cover the entire surface in a liquid layer 450 feet (137 metres) deep. 
article_snippet: To make the discovery, the scientists produced maps showing the distribution of normal water in the Martian atmosphere and 'heavy' water containing deuterium, a more massive form of hydrogen.
article_snippet: By analysing the ratio of 'heavy' to regular water the scientists showed that Mars must have lost a volume of water 6.5 times larger than the amount trapped in the present day polar ice caps.
article_snippet: It is possible that Mars once had even more water, some of which may have been deposited below the surface.
article_snippet: Because the new maps reveal microclimates and changes in the atmospheric water content over time, Mars once had
article_snippet: Missions like the Curiosity rover (illustrated) have shown that Mars was once wet for 1.5 billion years, but the scientists now think An ancient ocean on Mars containing the lost water had water for even longer.
article_snippet: This is longer than the time An ancient ocean on Mars containing the lost water took life on the Earth to arise, providing tantalising hints that Mars might once have been habitable .
highlights_snippet: Nasa Goddard scientists in Maryland studied past water on Mars .
  
highlights_snippet: But Nasa Goddard scientists in Maryland now know Mars was wet for more than 1.5 billion years .
  