In the Bahamas' submerged inland caverns, or "blue holes," a thin layer of fresh water separates oxygen from salt water. This creates a submerged, oxygen-free environment that could resemble underground water pockets on Mars or the seas of Europa.

In the blue holes of the Bahamas, the anoxic salt waters supports ecosystems that are completely unique to individual caverns. This diversity and ability to thrive in aquatic, oxygen-free environments could offer insights into both Earth's early conditions and the anatomy of extraterrestrial life that could exist within our solar system. Says astrobiologist Jenn Macalady of Penn State's Department of Geosciences:

The universe is made of the same elements and habitable planets are likely to share many of the same characteristics, like a temperature range conducive to life and the presence of water [...] We analyzed the DNA of microbes from five inland blue holes and didn't find any shared species [...] Some of these organisms use tricks we used to think were chemically impossible [...] If we can understand precisely how these microbes are making a living, we know what to look for on oxygen-free worlds.

Researchers eager to divine the geological and biological secrets of the blue holes have a race against time on their hands. Rising sea levels threaten to disrupt the holes' unique balance of salt and fresh water. You can read more about National Geographic's journey to the blue holes (including one named the Stargate!) here, and you can see more of Wes Skiles photography from the expedition here.

Thanks to Merilyn Terrell at Intelligent Travel for the heads up!

Could "blue holes" offer clues about the biology of extraterrestrials?

Could "blue holes" offer clues about the biology of extraterrestrials?


The Cascade Room in Dan's Cave on Sawmill Island.

Could "blue holes" offer clues about the biology of extraterrestrials?


The Cascade Room. You can see where the salt and fresh waters meet at the blurred halocline.

Could "blue holes" offer clues about the biology of extraterrestrials?


Ralph's Cave, Abaco.

Could "blue holes" offer clues about the biology of extraterrestrials?


Bright bacteria in the Sawmill Sink on Abaco. This bacteria produces toxic hydrogen sulfide, or "swamp gas."

Could "blue holes" offer clues about the biology of extraterrestrials?


[Graphic via National Geographic]