Okay, say we get our spacecraft and probes to Europa or some other icy world. What makes us think that life is even possible on these distant, shadowed, frozen worlds? Over the past few decades, scientists have been searching for life here on Earth in the wildest of places to see if life is possible just about everywhere, and the answer keeps turning out to be yes.

Now, in a new paper in Nature Geoscience, scientists have published the findings of samples taken of groundwater in a subsurface aquifer located between five and ninety meters below ground. Yes, life exists in water, but this team wanted to know if life could exist in water that gets no sunlight at all. Specifically, they looked for microbes that could carry out carbon fixation – chemosynthesis of carbon – to grow their biomass. And they found such microbes and a surprisingly high rate of carbon fixation as well. Lead author Will Overholt explains: The rates we measured were much higher than we anticipated. They equal carbon fixation rates measured in nutrient-poor marine surface waters and are up to six-fold greater than those observed in the lower zones of the sunlit open ocean, where there is just enough light for photosynthesis.

The microorganisms responsible for all this carbon fixation turned out to be uncharacterized and not closely related to any previously studied bacteria. Overholt notes: As food, these organisms are thought to form the basis of life for the entire groundwater ecosystem with all of its thousands of microbial species, similar to the role algae play in the oceans or plants on land.

So there is an entire functioning ecosystem in our groundwater that’s going to require a lot more research to understand. Amazing.

More Information

iDiv press release

“Carbon fixation rates in groundwater similar to those in oligotrophic marine systems,” Will A. Overholt et al., 2022 June 30, Nature Geoscience