Salt pond in Antarctica, among the saltiest waters on Earth, is fed from beneath

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November 15, 2017

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On the base of the Transantarctic Mountains lies a geological oddity. Don Juan Pond is among the saltiest our bodies of water on the planet, crammed with a dense, syrupy brine wealthy in calcium chloride that may stay liquid to minus 50 levels Celsius, far beneath the freezing level of water. However the supply of water and salt to this uncommon pond stays a thriller — at the same time as hints emerge that water in an identical type may exist on Mars.

A brand new College of Washington research makes use of the pond’s weird chemistry to pinpoint the water’s supply. The current paper, printed Sept. 15 in Earth and Planetary Science Letters, stories that it’s fed by a regional deep groundwater system and never, as beforehand prompt, from moisture seeping down from native valley slopes.

“Don Juan Pond might be one of the crucial fascinating ponds on Earth,” stated lead creator Jonathan Toner, a UW analysis assistant professor in Earth and area sciences. “After 60 years of in depth research, we nonetheless don’t actually know precisely the place it’s coming from, what drives the truth that it’s seen on the floor, and the way it’s altering.”

The perennial pond measures about 100 by 300 meters, the scale of some soccer fields, and is about 10 centimeters (4 inches) deep on common. It was first visited in 1961 and named after the expedition’s helicopter pilots, Donald Roe and John Hickey, incomes it the title Don Juan Pond. The distinctive salts within the pond decrease the freezing level, which is why this saline pond can exist in a spot the place the temperature ranges from minus 50 to plus 10 levels Celsius (-58 to +50 F).

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The pond was lengthy believed to be fed by deep groundwater. However then a high-profile 2013 paper prompt that near-surface moisture seeps, just like recurring slope lineae options lately noticed on Mars, had been transporting salts downhill to create the salt pond.

Toner is a geochemist specializing within the formation and properties of water in excessive environments on Earth, Mars and past. For the brand new research, Toner created a mannequin to compute how salty water modifications throughout evaporation, freezing, and with totally different water and salt inputs and outputs. In Antarctica’s appropriately named McMurdo Dry Valleys, water evaporation concentrates salts within the pond, which forces some salts to crystallize. These processes, together with inputs and outputs, trigger the pond’s water to alter over time.

Toner ran his mannequin for 2 conditions: one the place the water was gurgling up from beneath, and one other the place it was trickling down from near-surface seeps. Outcomes present that the noticed chemical make-up may solely be produced from beneath.

“You couldn’t get Don Juan Pond from these shallow groundwaters,” Toner stated. “It’s positively coming from the deep groundwater.”

His calculations additionally present that upwelling groundwater cycles by means of the pond each six months, that means the water should exit the pond by way of some unseen underground outflow.

The pond’s hydrology is necessary to geologists as a result of nowhere on Earth is extra just like Mars. The Pink Planet is extraordinarily chilly and dry, and the McMurdo Dry Valleys are one of many coldest and driest places on Earth.

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“If there may be water on Mars, it’s most likely going to look quite a bit like this pond,” Toner stated. “Understanding the way it shaped has massive implications for the place would you anticipate finding comparable environments on Mars.”

Latest research trace that liquid water would possibly exist on the floor of Mars, doubtlessly harboring life and even finally supporting long-term human settlements. The darker traces on steep slopes, which appear to be moisture streaks noticed above Don Juan Pond, might be brought on by an identical groundwater system.

Toner can be a part of a staff exploring Don Juan Pond and surrounding areas this December, sponsored by NASA and the Nationwide Science Basis. Researchers will spend six weeks tenting close to the pond and taking repeated chemical measurements of its liquid. They may also discover the close by slopes to measure the chemistry of the moisture seeps, and attempt to discover additional proof for the supply of salts to Don Juan Pond.

“If we settle for that the deep groundwater principle is true, then what we’re seeing might be a part of a much bigger course of that includes fairly an intensive aquifer,” Toner stated. “When desirous about the implications for the same atmosphere on Mars, that’s way more thrilling than only a localized floor phenomenon.”

The analysis was funded by NASA. Different co-authors are Ronald Sletten and David Catling within the UW Division of Earth & Area Sciences.

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For extra data, contact Toner at [email protected]

NASA grant: NNX15AP19G

Tag(s): Faculty of the Setting • Division of Earth and Area Sciences • geology • Jonathan Toner • polar science

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