The gradual disappearance of the water occurs when sunlight and chemistry turn water molecules into the hydrogen and oxygen atoms that they are made up of.
When they are broken down, Mars's weak gravity is unable to keep hold of them and they disappear off into space, according to the study, published in the journal Science.
Previous studies have showed the red planet was once flooded with flowing water, which has largely disappeared in its more recent history.
According to the findings, an international research team, led partly by Franck Montmessin from French National Centre for Scientific Research in France, just revealed that water vapour is accumulating in large quantities and unexpected proportions at an altitude of over 80 km in the Martian atmosphere.
It was found using the Trace Gas Orbiter probe that was sent to the red planet on board the ExoMars mission, run by the European Space Agency and its Russian counterpart Roscosmos.
Measurements showed that large atmospheric pockets are even in a state of supersaturation, with the atmosphere containing 10 to 100 times more water vapour than its temperature should theoretically allow.
With the observed supersaturation rates, the capacity of water to escape would greatly increase during certain seasons, the study said.
( With inputs from IANS )