How did this strange super-salty pond in Antarctica come into being?

Understanding the hydrological conditions of Don Juan pond in Antarctica (one of the saltiest water bodies on earth) will help scientists understand the mystery of the Martian environment. At the end of the world, in the cold Antarctic desert, NASA is located in a strange pond only a few inches deep. It is very salty and remains liquid even at the temperature of MINUS 58 degrees Fahrenheit (MINUS 50 degrees Celsius).

Since it was discovered in an expedition in 196 1 year, the extremely heavy and pure salt source of this pond has been a geochemical mystery. Scientists generally believe that the Tanghuang pond (named after the helicopter pilot of the expedition) is recharged by deep groundwater, but a widely publicized paper in 20 13 points out that these salts come from shallow sources.

In a new study published in the journal Earth and Planetary Science Letters on September 15, researchers questioned this discovery by using a computer model of pond chemistry.

Because this area is one of the closest terrestrial objects to Mars, understanding how water flows through the pond and surrounding areas can help scientists understand the behavior of similar features on this red planet. [7 places on earth that are most like Mars]

The salt in Don Juan's pond is different from that spilled on food. Instead, it is 95% calcium chloride, which significantly reduces the freezing point of water and helps the pond to remain liquid in the Antarctic winter.

The liquid in Don Juan pond in Wright Valley, Antarctica contains almost 45% salt by weight. (Pierre Roudier/Flickr) Jonathan Toner, a co-author of this study and a geochemist at the University of Washington, said that nature rarely produces such a pure aqueous solution. From a chemical point of view, Tona said, "It's like walking into a room and seeing a pink elephant."

All the salt makes the water thicker and more viscous than the water poured from the tap or rolled on the beach, making it have the consistency of dilute syrup.

The pond is so salty (about 40% by weight) because of the combination of two factors: the high evaporation rate in the extremely dry environment in mcmurdo dry valleys and the ability of calcium chloride to form a solution that is more concentrated than ordinary salt (sodium chloride). Why the chemical composition of the pond is so pure has always been a mystery. It is difficult for them to answer, because the pond is designated as a protected area to prevent any pollution, so there are restrictions on sampling and studying the area.

The study of 20 13 used time-lapse photography to monitor the water flow around the pond. The author concludes that when the humidity reaches the peak, calcium chloride in the surrounding soil will absorb water from the atmosphere, a process called deliquescence. On the hillside near the pond, the water looks like dark soil. The author thinks that periodic snowmelt will wash salt into the pond. Toner said, [Photographic evidence of climate change: delayed images of glacier retreat]

But we totally disagree with the author's conclusion. I think they really didn't take into account the past evidence about the source of deep groundwater.

He and his colleagues used a chemical model to compare two possible sources of deep salt groundwater with the process described in the paper of 20 13. This chemical model compares the composition of pond water with the evaporation from these two different sources.

Tona said that they found that the deep underground water source "matches it perfectly and is incredibly accurate", while the shallow water source "is not far from it".

This study still has the problem of where the deep groundwater finally comes from. Tona and his colleagues believe that salt water seeps from the frozen soil.