So on the same week that the highly-anticipated film “The Martian” opens in U.S. theaters (you are going to go see it, I assume) NASA revealed the latest discovery regarding the Red Planet: there is water on the surface there, salty rivulets that periodically run down steep slopes in Hale Crater and stain its sands with dark streaks.

It might not be something that Mark Watney would want to guzzle a glassful of, but it is a major finding for planetary scientists!

See actual HiRISE images of the locations traversed by Watney in “The Martian” here.

The news was released to the world on Monday, September 28, during a presser at NASA HQ in Washington DC. (You can see the full video below.) During the hour-long event NASA scientists and dignitaries John Grunsfeld, Jim Green, and Michael Meyer made the public affirmation that the typically drier-than-bone-dry surface of Mars does — at least in some locations — feel the wetness of liquid water to this day. The discovery was made with observations from NASA’s Mars Reconnaissance Orbiter (MRO) and research performed by Georgia Tech grad student Luju Ojha.

To make a long story short (you can read the full press release here) dark streaks that had been previously imaged by the HiRISE camera aboard MRO have been subsequently examined by another instrument aboard the orbiter and found to contain certain forms of salts (perchlorates) that can only be present in liquid water, and that also help keep water liquid at low temperatures.

The dark streaks are known as recurring slope lineae, or RSLs, because they have show up on satellite imagery as dark lines that appear and fade periodically with the Martian seasons, and are found mainly on steep slopes of craters and tall peaks.

RSLs have been observed by HiRISE for years and have long been suspected to be a result of flowing water, but the identification of hydrated perchlorates within them — the first such detection from orbit —  is the “dripping water gun” for the presence of liquid water.

Read more: What Happened to Mars’ Water?

So what does this mean for Mars and future human exploration?

For one thing it gives a target for where to look for the possibility of life on the surface of Mars. Here on Earth where there’s water there’s nearly always some sort of life that uses it to survive, and the same may be said for Mars (not to mention elsewhere in the Solar System.) And even if life isn’t crawling around literally on top of Mars, the source of the water — whatever that may prove to be — could be located at a safe enough distance from the harshness of the Martian surface to support life.

“It’s very likely I think that there’s life in the crust of Mars, as microbes,” stated Alfred McEwen, principal investigator for the HiRISE instrument, during Monday’s press conference.

And with the presence of water comes potential resources for future explorers, in the form of drinking and irrigation water (properly desalinated, of course) and the base ingredients for rocket fuel: hydrogen and oxygen.

“Water…may decrease the cost and increase the resilience of human exploration on the Red Planet.”
— Mary Beth Wilhelm, NASA’s Ames Research Facility

Of course these damp, salty streaks in the Martian sand are far from actual streams, rivers, or oceans, but they are our best hints at hidden reservoirs on the Red Planet.