The Saltiest Pond on Earth Could Explain How Bodies of Water Form on Mars

At 40 percent salinity, the pond is the saltiest body of water on the planet.

Don Juan Pond isn’t just an awesomely assonant name for a little pool of water; it’s also the name of one of the most interesting ponds out there for astrobiologists. At 40 percent salinity, the pond is the saltiest body of water on the planet. It’s 18 times saltier than the ocean. Even though it’s in Antarctica, it’s so salty that it never freezes in conditions that get to 40 degrees below zero. But how does it get all that salt? New research from Brown University seems to have uncovered the answer, and it could mean that ponds like Don Juan Pond are possible on Mars.

The researchers took a simple approach—taking lots and lots of pictures of the pond—and discovered a couple of its water sourcees. Brown University’s press release puts it this way:

What the pictures showed was that water levels in the pond increase in pulses that coincide with daily peaks in temperature, suggesting that the water comes partly from snow warmed just enough by the midday sun to melt. But that influx of fresh water doesn’t explain the pond’s high salt content, which is eight times higher than that of the Dead Sea. For that explanation, the researchers looked to a second source of liquid documented in the photos.

The second source comes from a channel of loose sediment located to the west of the pond. Previous research had found that sediment to be high in calcium chloride salt. To see if that was the source of the pond’s salt, the researchers set up a second time-lapse camera to monitor the channel and synchronized the pictures with data collected from nearby weather stations.

Looking back at the pictures, they saw that these water tracks were formed by salt in the soil absorbing water from the air. The tracks trickle down to the pond and, voila, salty water.

This isn’t just a one-off, wacky case of geology either, the researchers say. It could help us to understand Mars a little better. The Huffington Post explains:

The water tracks around Don Juan Pond look strikingly similar to features recently found on Mars known as recurring slope lineae. The Martian clusters of dark, narrow lines periodically appear and grow on slopes and cliff faces in the Red Planet’s warmer regions. Some scientists have taken them to be evidence of occasional flows of briny water on Mars today.

What’s more, chloride-bearing salts have been detected on Mars, which would be capable of the same kind deliquescence seen in Antarctica, the researchers note. The new study also found that Don Juan Pond manages to stay wet without being supplied groundwater, which is not thought to exist on Mars today.

“Broadly speaking, all the ingredients are there for a Don Juan Pond-type hydrology on Mars,” Dickson said.

So understanding how Don Juan Pond forms could mean understanding how bodies of water like this could form on Mars. And if we can find life in Don Juan Pond, then life could exist on our red neighbor as well.

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