Don Juan Pond, Antarctica Credit: University of Georgia
Don Juan Pond is not what it sounds like. It’s not for the duckies. It’s definitely not for lovers, although some people find its environment beautiful, in a stark sort of way. Don Juan Pond is in Antarctica, in the Dry Valleys between the Asgard Range and the Dais Range in Victoria Land. It’s one of the coldest regions of Earth, but this pond rarely, if ever, freezes. That’s because it is the saltiest body of water on the planet. With a salinity level of over 40% (hypersaline) it’s 18 times more salty than the oceans. It is fed by equally mineralized ground water, which in the past decades since discovery in 1961 has decreased until the pond is now almost dry. So it’s a bit of a geological freak. What else?
Two things: First, as recently discovered by a team from the University of Georgia (USA) and reported in Nature Geoscience, the pond produces nitrous oxide (laughing gas), which is often an indicator of microbial activity. Second, this same type of brine pool in an extreme cold environment would be characteristic for Mars.
Although when it was first discovered Don Juan Pond had a microflora of bacteria, yeast, blue-green algae, and fungi; they are gone now. As it turned out, the researchers found a non-organic source for the nitrous oxide. The interaction of the brine (salt) solution of the pond with the rock of the area (especially basalt, of volcanic origin) generates a variety of products including nitrous oxide and hydrogen. While there appears to be currently no living organisms in the pond, the brine-rock interaction produces chemicals and gases that are considered viable for some kinds of extremophiles organisms.
This is significant, because it is believed that if there is any standing (unfrozen) water on Mars, it will be in the form of brine pools much like Don Juan Pond. The nitrous oxide produced at the pond could indicate a mechanism by which a nitrogen cycle, generally a sign of organic activity, might be preserved on Mars. The hydrogen could be the basis for life by chemosynthesis, using chemicals such as hydrogen and sulfur instead of photosynthesis.
Obviously, this is an area begging for more research. The research at Don Juan Pond continues, looking for details in the chemical production. There may be other such water conditions on Earth, if they can be found. Of course, the big prize is to locate and eventually analyze brine pools (above or below ground) that may exist on Mars.