Mars is streaky (Photo: NASA/JPL/University of Arizona)

After teasing the world with the announcement that a “Mars mystery” had been solved (and after news outlets that likely knew the embargoed study teased the answer), NASA revealed its big find: water on Mars.

Specifically, they reported that Mars’ strange streaks are caused by salty water flowing on the planet’s surface.

These streaks, called slope linear, appear seasonally. When Mars heats up, to a balmy 250 to 300 degrees Kelvin, the streaks appear—they can be as wide as 16 feet or so. (For context, the freezing point of water is 273.2 degrees Kelvin.)

This is surprising because the surface of Mars is not a friendly place to water. Even if it was there, and even if it did melt, it wouldn’t necessary flow in nice lines down the surface; it’d evaporate first.

Water mixed with other compounds, though, behaves differently. The various characteristics of the strange streaks, NASA scientists report in a Nature Geoscience paper, “suggest a possible role of salts in lowering the freezing point of water, allowing briny solutions to flow.” They analyzed data from the Compact Reconnaissance Imaging Spectrometer for Mars, which indicate what kind of compounds are present on the planet’s surface, and found that the salts in the streaks backed up the idea that the lines were caused by flowing, briny water. 

Even before NASA officially released this information, though, science reporters were talking about water on Mars and pointing as evidence to two papers, authored by members of the same team and being presented at a conference today. One paper is an attenuated version of the paper published in Nature Geoscience. The other deals with the possible origins of the water. In the Geoscience paper, the authors write that “The origin of water forming the [streaks] is not understood,” but in the conference paper, some of them suggest that the water could come from the atmosphere.

That’s only one possible explanation for the water’s origins, but the team is confident that it’s there. But that still doesn’t answer the most intriguing question about Mars: Is anything living there? 

Bonus find: A “murder victim” who’s been hiding for 31 years, a really old Russian road

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