Dry Valley Tour: Part II
To continue on the theme of intriguing landscapes, I would like to introduce you to Don Juan Pond.
From a helicopter, Don Juan Pond may look like a meltwater pool, but is in fact groundwater fed and extremely hypersaline. It is located in Wright Valley, just north of Taylor Valley, and just to the west of Lake Vanda. We visit the pond annually to record lake level.
Hypersalinity (defined as having a higher salt content than the ocean) is common in the Dry Valleys. Lake Fryxell and Lake Bonney both have high salt contents, but their bottom water was originally derived from the ocean and mostly consists of NaCl (sodium chloride, like the ocean). Interestingly, the thick brine of Don Juan Pond is 40% salt and mostly CaCl2 (calcium chloride). This gives is the honour of being the SALTIEST WATER ON EARTH!!
Yes, it is saltier than the bottom of the Mediterranean or the Dead Sea. At 40% salt, it has a salinity 18x that of the ocean and a freezing point ~ -50°C. Even in Antarctica, the pond never freezes.
Recently, some interesting publications have been written on the geochemistry of the pond. It turns out that pond gives off a large flux of nitrous oxide (laughing gas, also a potent greenhouse gas). Under most circumstances, biological reactions drive the production of nitrous oxide. However, at Don Juan Pond, the gas is produced abiotically by a reaction between the local rock and the brine. This discovery is a new link between atmospheric gases and rocks!