Deep, deep beneath the ocean waves (USGS/NOAA)

Well, ok, perhaps it's not life really in liquid carbon dioxide, but as you'll see it's pretty close. The study of extreme environments on Earth plays a big role in our expanding knowledge about places that support life but are radically different from the sunny, temperate, beer swilling, tea drinking surroundings we find ourselves in. As such these may represent good analogs to certain spots on worlds like Mars, Europa, Enceladus, or even further afield. Some of the most remarkable and provocative discoveries of extreme conditions have been those around deep ocean hydrothermal vent systems. Often located on or near to the planet-straddling mid-ocean volcanic ridges these are places where water has been siphoned into the sub-seafloor, superheated and enriched with all manner of soluble compounds (like metal sulphides, which are very bad for our delicate constitutions but just the stuff for chemoautotrophic organisms) before being squirted back out into the chill marine environment at depths of over a kilometer. Down here the ambient temperature is about 3 Celsius, and pressures can be hundreds of times that at the Earth's surface. As the chemically rich water, often at temperatures of over several hundred degrees, sprays out into this dark cold environment it not only quickly deposits minerals but it provides oases for some of the most bizarre and unexpected ecosystems we have discovered. From extremophilic archaea and bacteria, to their symbiotic relationship with creatures like tube-worms, these locations flourish in the abyssal gloom.

The video below is to my mind an excellent illustration of just how alien these places can be. It's one that I've used over the past few years in talks and classes to get the point across. This footage was taken by a robotic submersible 1.6 kilometers down at a so-called "white smoker" vent system on one side of the small undersea volcano called Eifuku in the Japanese volcano chain. White smokers (as opposed to "black smokers") are not the hottest of hydrothermal vents, and are white due to the mix of calcium, barium, and silicon compounds in their water. This site, called "Champagne" for reasons that will become immediately apparent, is also pumping out lots of carbon dioxide from the underlying volcanic system. But at these pressure depths and concentrations the carbon dioxide exists as neither gas nor solid, the bubbles you see in the movie are liquid CO2.

Watch the movie through and note the parts where the remote controlled machine is being moved and wiggled in an effort to shake loose the bubbles. Apparently liquid CO2 is not only surprisingly buoyant in ocean water, it is also sticky stuff.

And the evidence of life? Well, pay attention at 38 seconds into the show. With utter disregard for the extraordinary environment a shrimp-like creature swims purposefully under the robot and exits stage lower right. It may not live in liquid CO2, but it doesn't seem bothered by it in the slightest. We must also assume that it's finding plenty of food within this bubbling environment.

For more on the exploration of these alien places right beneath our noses, take a look at this NOAA Ocean explorer site.