Water Cycle in Martian Atmosphere (IMAGE) CNRS Caption When the sun lights up the large reservoirs of ice at the poles, water vapor is released into the atmosphere. These water molecules are then transported by winds toward higher and colder altitudes where, in the presence of dust particles, they can condense into clouds and prevent a rapid and mass progression of water toward higher altitudes (as on Earth). On Mars condensation is often hindered. The atmosphere is thus regularly supersaturated in water vapor, which allows even more water to reach the upper atmosphere, where the sun's UV rays disassociate them into atoms. The discovery of the increased presence of water vapor at very high altitude entails that a greater number of hydrogen and oxygen atoms are able to escape from Mars, amplifying the loss of Martian water over the long term. Credit © ESA Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.