The Saltiest Lake on Earth
New findings that have implications for similar briney features, known as recurring slope lineae (RSL), found on Mars. “Thus, if RSL and chloride-bearing basin floor units on Mars do represent DJP-like hydrologic systems, they may have significant potential for hosting resilient microbiota, and the most habitable places on Mars may mimic the least habitable places on Earth.”
Originally shared by Gary Ray R
The Lake in Antarctica That Does Not Freeze
There are lakes on the frozen continent of Antarctica. Most have thick layers of ice year round but there is one that has so much salt that the water does not freeze, even in the frigid depths of winter in the coldest area on earth. Well, not a really big lake but just a pond; it is the Don Juan Pond located in the west end of Wright Valley (South Fork), Victoria Land, Antarctica. Where does the salt come from?
Don Juan Pond, also called Lake Don Juan, is a small and very shallow hypersaline lake in the west end of Wright Valley (South Fork), Victoria Land, Antarctica, 9 kilometers (5.6 mi) west from Lake Vanda. It is wedged between the Asgard Range in the south and the Dais in the north. On the west end there is a small tributary and a feature that has been described as a rock glacier. With a salinity level of over 40%, Don Juan Pond is the saltiest known body of water on Earth. ⓐ
Don Juan Pond was discovered in 1961. It was named for two helicopter pilots, Lt Don Roe and Lt John Hickey, who piloted the helicopter involved with the first field party investigating the pond. On that initial investigation, the temperature was −30 °C (−22 °F) and the water remained in a liquid state. ⓐ
While discovered in 1961, it is in the news now because of the images just released by NASA taken by the Earth Observatory satellite. One of the images is shown below on the right.
The image on the left is from the 2013 study done by researchers by James Dickson and James Head from Brown, Joseph Levy from Oregon State, and David Marchant from Boston University. They were investigating the source of the calcium chloride salt. (both pictures are high resolution so have a closer look)
The research represents the most detailed observations ever made of Don Juan Pond. “It was a simple idea,” Dickson said of the team’s approach. “Let’s take 16,000 pictures of this pond over the course of two months and then see which way the water’s flowing. So we took the pictures, correlated them to the other measurements we were taking, and the story told itself.” ⓑ
Using time lapse photography and other data, the researchers show that water sucked out of the atmosphere by parched, salty soil is the source of the saltwater brine that keeps the pond from freezing. Combine that with some fresh water flowing in from melting snow, and you’ve got a pond able to remain fluid in one of the coldest and driest places on Earth. And because of the similarities between the Dry Valleys and the frozen desert of Mars, the findings could have important implications for water flow on the Red Planet both in the past and maybe in the present. ⓑ
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. ⓑ
The pictures show dark streaks of moisture called water tracks forming in the soil whenever the relative humidity in the air spiked. Similar water tracks also form on a cliff face north of the pond. What’s forming these tracks is the salt in the soil absorbing any available moisture in the air, a process known as deliquescence. Those water-laden salts then trickle down through the loose soil until they reach the permafrost layer below. There they sit until the occasional flow of snowmelt washes the salts down the channel and into the pond. ⓑ
When the team saw how closely correlated the appearance of water tracks was to their humidity readings, they knew the tracks were the result of deliquescence and that the process was key to keeping the pond salty enough to persist. ⓑ
The findings refute the dominant interpretation of Don Juan Pond’s origin. Since the pond’s discovery in 1961, most researchers had agreed that its briney waters must be supplied mainly from deep in the ground. However, these new images show no evidence at all that groundwater contributes to the pond. ⓑ
ⓑ News from Brown
How the world’s saltiest pond gets its salt
Scientific Reports (open access)
Don Juan Pond, Antarctica: Near-surface CaCl2-brine feeding Earth’s most saline lake and implications for Mars
World’s Saltiest Body of Water Seen from Space (Photo)
Image on right,
Credit: NASA Earth Observatory image by Jesse Allen, using EO-1 ALI data provided courtesy of the NASA EO-1 team and the U.S. Geological Survey.
NASA Earth-Observing Satellite photo showing Don Juan Pond, a network of channels carved into the bedrock east of the Wright Upper Glacier, and the frozen Lake Vanda to the northeast of the pond.
Image on left,
Credit: Geological Sciences/Brown University
A camera installed above Don Juan Pond in Antarctica’s McMurdo Dry Valleys took 16,000 images in two months, documenting geological processes in real time.