Water on Mars: Flowing salt water discovered on the Red Planet

NASA's Mars Reconnaissance Orbiter has confirmed that mysterious lines on the surface of the planet are evidence of liquid water. CNET's Eric Mack spoke to the scientist behind the groundbreaking discovery.

Eric Mack Contributing Editor
Eric Mack has been a CNET contributor since 2011. Eric and his family live 100% energy and water independent on his off-grid compound in the New Mexico desert. Eric uses his passion for writing about energy, renewables, science and climate to bring educational content to life on topics around the solar panel and deregulated energy industries. Eric helps consumers by demystifying solar, battery, renewable energy, energy choice concepts, and also reviews solar installers. Previously, Eric covered space, science, climate change and all things futuristic. His encrypted email for tips is ericcmack@protonmail.com.
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Eric Mack
4 min read

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This false-color image shows dark lines running down Martian slopes caused by flowing salt water. NASA/JPL/University of Arizona

We can't say for sure that Mars harbors all the necessary ingredients to support life, but a new landmark finding strengthens the case that flowing, liquid Martian water could sustain life on the Red Planet and perhaps one day, us too.

It's not quite the Dead Sea or the Great Salt Lake, but it is the confirmation Lujendra Ojha has been looking for the past few years -- that there is flowing, briny water on or near the surface of Mars. Ojha is the Georgia Tech graduate student who first helped spot so-called " recurring slope lineae" (RSL) when he was just an undergrad. RSL are seasonal dark, finger-shaped markings on Martian slopes that look an awful lot like liquid flowing downhill to create wet sand or soil.

"This is the smoking gun," Ojha told CNET. "This is as good as we're going to get with the current technology."

That technology is the Mars Reconnaissance Orbiter (MRO), which has been circling and surveying the planet for nearly a decade. Ojha was part of the team that originally spotted such markings in MRO photos in 2011. Now, he's the lead author on a paper published online Monday in Nature Geoscience that lays out a new spectral analysis of MRO data and finds evidence of hydrated salts in those dark, wet-looking lines on Mars.

Evidence points to flow of briny water on Mars (photos)

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"What we're observing here is the spectroscopic signature of perchlorates that are hydrated by water," he explained to me via phone from France on Sunday. "These perchlorate salts have salt crystals that have molecules of water in them."

Spying these salts strongly suggests the mystery dark lines on Mars really are as wet as they look, according to Ojha and his co-authors.

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These wet streaks are a few hundred meters long on the walls of Mars' Garni Crater. NASA/JPL/University of Arizona

We see hydrated salts occur naturally here on Earth. One well-known example derives its name from an English spring where compounds from local rock and soil dissolve in ground water, float around for a bit, then bind together to create salt molecules that hydrate with the water's molecules. Boil down that water and what remains is known as Epsom salt.

The paper draws a comparison between the apparently wet lines on Mars and Chile's Atacama Desert, one of the driest places on Earth, where similar salts offer the desert's "only known refuge for active microbial communities and halophylic prokaryotes."

Ojha cautions that this doesn't mean the briny waters that appear to be flowing on Mars are teeming with microscopic life, because they may just be too intermittent to support anything.

"But what we're saying is that compared to most of Mars in the present day climate, these places (where RSL have been spotted) are probably more habitable than most of the rest of the planet, which is completely bone dry."

The revelation of apparent flowing brines on our neighbor might begin to solve the mystery of what causes RSL, but it also opens up a whole new batch of questions.

Because the lines seem to emerge seasonally and then apparently dry up and disappear, scientists now wonder what is recharging the source year after year. Could it be some sort of hidden spring or aquifer? Perhaps melting water ice?

Another paper (PDF) being presented Monday suggests that the Martian atmosphere itself might be the source of the salty flows. The basic idea behind this hypothesis is that RSL sites are found in a really diverse set of locations on Mars, including spots and elevations where aquifers or ice would seem less likely to exist. Lead author Alfred McEwen is also the lead scientist for the MRO's high-resolution imager, and Ojha is also a co-author.

There's also the question of what the RSL look like at different times of the Martian day. As Ojha explains it, all the MRO's observations of the lines have been taken at mid-afternoon. He suggests that different technology might allow scientists to see what they look like at cooler times of day.

"We might actually be able to see the spectroscopic signature of liquid water," he told me. "But this result is unambiguous that liquid water does play a big, big, big role in the formation of RSL on Mars."

And then there's the other big question many of my fellow sci-fi freaks are surely asking themselves already: What does this mean for the potential of a future human colony on Mars?

"How is this resource, this liquid water on the surface going to help humanity in the long run?" Ojha wondered aloud rhetorically when we spoke. "One century's magic is another century's science. We're saying that there is water and it could probably be used as a resource for the future of humanity."

I think he's talking about more than just making pickles with Martian mountain brine, but I'd sure love to sample a few of those at my first Red Planet tailgate party.