Evidence of water has fed scientific debates on the possibility of life on Mars for centuries.
A well-known twentieth-century astronomer, Percival Lowell, spent his career mapping what he believed were irrigation canals built by Martians.
His findings have been proven false, but there are dry channels on Mars that look like they were created by water erosion.
There is also evidence of ancient flooding.
While water does not now exist on Mars in its liquid form, it does appear as a solid and as vapor.
The northern ice cap is partially ice and sometimes frost, fog, and water vapor clouds appear.
The most prominent features on Mars are the northern polar ice cap; the planet’s largest volcano, Mons Olympus; lines that astronomer Percival Lowell mistook for canals; and the Vallis Marinaris, the largest canyon system.