The European Space Agency's Mars Express and NASA's Mars Reconnaissance Orbiter have detected signs that liquid water once flowed in both southern and northern regions of the planet, an ESA release said Friday.
Until recently, data showed that only the Southern Hemisphere exhibited signs of having once been warmer and wetter that it is today, the agency said.
But new data from the orbiters show rock formations altered by water exist in the Northern Hemisphere as well.
The Mars Express sensors first detected the mineral deposits, a finding confirmed by a higher-resolution sensor on the National Aeronautics and Space Administration orbiter.
"We can now say that the planet was altered on a global scale by liquid water more than 4 billion years ago," John Carter of the University of Paris said.
The new findings may suggest sites for future exploratory landers in the search for the evolution of primitive life on the planet, the ESA said.