Hydrated silicate minerals were found by the ESA's Mars Express and NASA's Mars Reconnaissance orbiters in northern lowlands of the Red Planet, a clear indication that water once flowed there, ESA said in a statement Friday ahead of the publication of a study in journal Science.
Water was present on the surface of Mars four billion years ago but lasted for only a few hundred million years, according to principal investigator Jean-Pierre Bibring from the University of Paris.
"It shows that there was water, but not in the form of a large ocean", Bibring said, adding that the Martian crust was hydrated in the same manner in the north and south.
The conclusions contradict those of an American team, who in a study published June 13 in Nature Geoscience journal said a vast ocean covered a third of the surface 3.5 billion years ago.
"Mars had already lost its atmosphere 3.5 billion years ago, water was no longer stable in the liquid state on the surface," said Bibring.
"Huge streams were able to flow, but the lack of surface water meant permanent oceans could not be fed," he said.
"If the pressure and the temperature would not permit water to exist in a stable liquid state, some would evaporate and leave the planet, while water could also enter the soil," he said.
"It could remain on the surface for days or weeks, but not millions of years," he said.
The hydrated silicate minerals were found in sizeable impact craters in the northern plains which punched down several kilometers, exposing ancient crustal material.
The ESA had previously discovered similar minerals in the southern highlands