Water on the surface of Mars is conserved in rocks. The cessation of tectonic activity on the Red Planet stopped the circulation of water from the atmosphere back to the surface.
Lakes, oceans and rivers washed the entire surface of Mars 4 billion years ago, but the planet dried out irrevocably as a result of stopping the movement of the lithosphere, Science magazine reports. River beds and basins of lakes and oceans are still preserved on the surface of the planet.
All the water on Mars did not completely evaporate and leave the planet, as previously thought, but remained in the form of huge reservoirs of ancient hydrated minerals and ice.
Most of the ice is below the surface of the planet, the rest is in craters and polar caps, where temperatures are maintained that prevent evaporation. In addition to ice, water was also discovered in liquid form under the icy surface of the South Polar Cap.
The authors of the study, using data from Mars rovers and orbital stations, concluded that from 30 to 90 percent of the water on Mars was absorbed by rocks through the process of weathering and water accumulation (hydration).