Scientists find new evidence of flowing salt water on Mars

It’s been a big week for space-related news, and it’s only Monday. Sunday night, we feasted our eyes on the Super Blood Moon. And NASA teased us on Twitter, saying it had a “major scientific finding” about the “mysterious” world of Mars to unveil at a press conference Monday at 11:30 a.m. ET. That sent the world into a speculation spiral over what it could be. Water? Perhaps early signs of life?

Well, this morning we’re getting an early big clue thanks to a new paper in the journal Nature Geoscience. It appears that scientists have found the most direct evidence to date of liquid water currently on Mars. That’s HUGE!

“Water is essential to life as we know it,” the authors write in the paper. “The presence of liquid water on Mars today has astrobiological, geologic and hydrologic implications and may affect future human exploration.”

Take a minute to wrap your head around that so we can get into the science. Okay.

To be exact, the team of scientists found briny flows at four different locations on Mars’ surface, all at dark streaks, called recurring slope lineae that have long intrigued planetary scientists. They flow downhill and appear only during the Martian spring and summer, when temperatures hover between roughly -10 and 80 degrees Fahrenheit. Then, they vanish in winter.

Scientists have long thought that these thin, river-like structures were formed by frozen water trapped in soil that was heated by warming temperatures and then started flowing downhill, a theory today’s study supports. In some instances, the surrounding rock would have been below water’s freezing temperature, but that’s where the briny in briny flows becomes important.

Water typically freezes at 32 degrees Fahrenheit on Earth, but when salts get dissolved in water, that lowers the freezing point, so it stays liquid at colder temperatures. That’s why people “salt” the streets in winter. They’re preventing black ice from forming! (In the winter, these structures disappear all together because the initial font of flowing water wouldn’t form because the temperature was too cold.)

When they analyzed these Martian formations, scientists found some evidence of several different types of salts. And the salts were hydrated, meaning they had water around them. (Most of the water had boiled off already, so what they were detecting was water trapped by the salts.) The water on Mars’ surface could amount to several Olympic swimming pools worth, but spread out over a really big area, NASA scientists said during today’s press conference. The spidery recurring sloping lineae are super long, but only a few meters wide.

They didn’t take samples from the recurring slope lineae. Instead, they used images captured by an instrument called the Compact Reconnaissance Imaging Spectrometer for Mars—or CRISM, for short—aboard the Mars Reconnaissance Orbiter, a spacecraft launched in 2005 whose main mission was to find evidence of water on the surface of Mars. Then, they analyzed these images for the presence of water and salts based on the play of light in the photos.

In the past, the makeup of recurring slope lineae had been difficult to analyze because they’re so small, and images of them are taken from kilometers up above the Martian surface. To make their job easier, scientists chose locations, like Palikir crater, where these structures tend to be longer and wider. Plus, they developed more powerful algorithms that were able to detect differences in the way water and salts reflect and absorb light, down to the individual pixel level.

The findings are good news for anyone with hopes of finding life on Mars. And in the long-term, it breathes some life into the aspirations of people wanting to visit, or settle, the rocky planet. ICYMI, that’s a fair number of people. There’s a space travel renaissance happening, and Mars is at its center. Ordinary citizens are volunteering for one-way journeys to Mars. Elon Musk wants to build a colony there. NASA wants to send a manned mission there someday. Even Hollywood is cashing in on the Mars action, with the upcoming movie The Martian, which comes out Friday.

But before you go signing up for space travel, remember this: Mars’ liquid water wouldn’t be potable. It’s chockfull of perchlorates, according to the study. Here on Earth, these highly chlorinated salts have been found in drinking water sources in Canada and the U.S. and have been associated with thyroid problems. In 2009, scientists called perchlorate “an emerging chemical of concern.” The absence of drinking water on Mars has been viewed as an obstacle to Mars colonization. Humans can’t survive without it, so astronauts would have to take water with them from Earth. Water is heavy, so it makes the 35 million-mile journey that much more expensive. Today’s findings don’t change that. Martian explorers would have to find fresh water for Mars to be a viable habitat.

Evidence of water on Mars has been reported before. In 2011, the Opportunity Rover found gypsum, a mineral scientists said at the time could only have been deposited by liquid water. The following year, Curiosity found evidence of an ancient Martian river. There’s evidence of frozen ice currently at its poles. Earlier this year, scientists even found some indirect evidence of a Martian water cycle and the formation of liquid water at night. But to date, this is the strongest evidence for contemporary liquid H20 on the planet. The next biggest news would be a human—or a roboastronaut—seeing and collecting water first hand. But until that happens, this is pretty exciting.

At today’s press briefing, scientists discussed findings described in the Nature Geoscience paper, as well as some of the implications. They said, for instance, that this will help them home in on potential spots on Mars that are habitable. So far, only 3-4% of Mars surface has been mapped, so looking for life there is like looking for keys in a dark place.

Scientists also said that they still don’t know where the water is coming from, so that will be the next question they seek to answer.

While they do that, you can bask in the awesomeness of Mars’ salty water flows, complete with a new video from NASA:

Update 9:35 a.m. PT: The story has been updated to include information from today’s press briefing.

Daniela Hernandez is a senior writer at Fusion. She likes science, robots, pugs, and coffee.