The strongest evidence we have yet for liquid water on Mars is most closely related to one common Martian feature, a team of scientists recently reported in the journal Nature Geosciences.
That feature, called recurring slope linae - Latin for "line" - refers to long, dark flows that point downhill and, more importantly, contain salts that harbor crystals of liquid water.
One of the instruments the team used for their recent discovery was the HiRISE camera on board the Mars Reconnaissance Orbiter, which has taken photos of all the different locations on Mars where recurring slope linae appear, and consequently, where liquid water recently flowed on the Martian surface.
Because you need relatively warm temperatures for liquid water, all of these places are near the Martian equator. Here's where scientists think there is liquid water on Mars: