There is enormous evidence that water once flowed in river valleys on Mars.
 Images of curved channels have been seen in images from Mars spacecraft dating back to the early seventies with the Mariner 9 orbiter.
 Indeed, a study published in June 2017, calculated that the volume of water needed to carve all the channels on Mars was even larger than the proposed ocean that the planet may have had.
 Water was probably recycled many times from the ocean to rainfall around Mars.
 The pictures below show a channels in Newton Crater.
There is enormous evidence that water once flowed in river valleys on Mars.  Images of curved channels have been seen in images from Mars spacecraft dating back to the early seventies with the Mariner 9 orbiter.  Indeed, a study published in June 2017, calculated that the volume of water needed to carve all the channels on Mars was even larger than the proposed ocean that the planet may have had.  Water was probably recycled many times from the ocean to rainfall around Mars.  The pictures below show a channels in Newton Crater.
Newton (Martian crater)