( CNN ) Scientists at NASA are one step closer to understanding how much water could have existed on primeval Mars . These new findings also indicate how primitive water reservoirs there could have evolved over billions of years , indicating that early oceans on the Red Planet might have held more water than Earth 's Arctic Ocean , NASA scientists reveal in a study published Friday in the journal Science . `` Our study provides a solid estimate of how much water Mars once had , by determining how much water was lost to space , '' said Geronimo Villanueva , a scientist at NASA 's Goddard Space Flight Center . `` With this work , we can better understand the history of water on Mars . '' To find answers to this age-old question about Martian water molecules , scientists used the world 's three major infrared telescopes , in Chile and Hawaii , to measure traces of water in the planet 's atmosphere over a range of areas and seasons , spanning from March 2008 to January 2014 . `` From the ground , we could take a snapshot of the whole hemisphere on a single night , '' said Goddard 's Michael Mumma . Scientists looked at the ratio of two different forms -- or isotopes -- of water , H2O and HDO . The latter is made heavier by one of its hydrogen atoms , called deuterium , which has a neutron at its core in addition to the proton that all hydrogen atoms have . That weighed down HDO more , while larger amounts of hydrogen from H2O floated into the atmosphere , broke away from Mars ' low gravity and disappeared into space . As a result , water trapped in Mars ' polar ice caps has a much higher level of HDO than fluid water on Earth does , the scientists said . The scientists compared the ratio of H2O to HDO in Mars ' atmosphere today to the ratio of the two molecules trapped inside a Mars meteorite , a stone that broke off from Mars -- perhaps when an asteroid hit -- and landed on Earth some 4.5 billion years ago . They were able to determine how much that ratio had changed over time and estimate how much water has disappeared from Mars -- about 87 % . The findings indicate that the Red Planet could have had its fair share of blue waters , possibly even yielding an ocean . According to NASA , there might have been enough water to cover up to 20 % of Mars ' surface . That would amount to an ocean proportionally larger than the Atlantic on Earth . `` This ocean had a maximum depth of around 5,000 feet or around one mile deep , '' said Villanueva . NASA scientists say that much of this water loss happened over billions of years , along with a loss of atmosphere . And as the planet 's atmospheric pressure dropped , it was harder for water to stay in liquid form . Heat also contributed to its evaporation . As a result , the remaining primeval ocean water continued to move toward the poles , where it eventually froze . `` With Mars losing that much water , the planet was very likely wet for a longer period of time than was previously thought , suggesting it might have been habitable for longer , '' said Mumma . CNN 's Ben Brumfield contributed to this report .
Scientists measured water in Mars ' atmosphere with ultra giant infrared telescopes . They compared the ratio of certain molecules on the planet with that of a Mars comet that landed on earth .