Skip to main content
Researchers are in search of extremophiles deep below the earth’s surface
Erin Broberg

It’s not all cleanrooms and Tyvek suits at Sanford Underground Research Facility (Sanford Lab). Sometimes, it’s muck boots and headlamps. Last week, visiting biologists stepped off the cage onto the 1700 Level of Sanford Lab. From there, the team motored via trolley through the drift, took ATVs down a ramp and walked a mile through shin-deep water by the light of their headlamps to reach a collection site on the 2000 Level.

These researchers were in search of inhabitants that live deep below the earth's surface.

“We are studying subsurface samples to learn how microbes are metabolizing and surviving in those locations to help us understand how life might be functioning on other planets that experience the same or similar stressors, like extreme heat, temperature, pressure, radiation and lack of sunlight,” said Brittany Kruger, field work coordinator and assistant research scientist with the Desert Research Institute in Las Vegas, Nevada. In an earlier phase of the project, the team collected samples from other extreme environments, including wells near Death Valley, naturally-occurring springs in Northern California and deep ocean environments.

Sanford Lab, with over 370 miles of shafts, drifts and ramps, serves the project as DeMMO, or the Deep Mine Microbial Observatory. The DeMMO effort is run by Dr. Maggie Osburn at Northwestern University, who conceptualized and established the DeMMO site. The project began as a NASA astrobiology-funded effort and is now supported by NASA's exobiology program and other partners.

The observatory at Sanford Lab is a network of boreholes that intersect fluid-filled fractures on the 800, 2000, 3950 and 4850 levels. Kruger visits two to three times a year to collect samples from the various boreholes. 

“Each borehole we visit is very different in terms of microbiology,” said Kruger. “The differences are not only dependent upon depth, but also on the chemistry of the water that flows through the site.”

Once the team has collected samples, they spend hours processing them.

“At each DeMMO borehole, we do a suite of both biological and chemical analyses sample collecting,” said Kruger. Some chemical analyses are completed in situ, while other samples are collected in bottles with preservative to be analyzed in a lab. The chemical analysis helps researchers understand the specific environment in which the microbes are living.

“In terms of microbiology, we take a two-part approach,” Kruger explained. “We take raw water back to the lab to try to grow microbes from that water sample. We also filter the water to collect and concentrate cells.” By concentrating the cells, researchers can do a roll call via DNA analysis to understand which species are present and how the community is functioning.

“With each sample, we are finding thousands of species," Kruger said. "The vast majority overlap with samples we or others have collected elsewhere. That being said, every time we take a sample, we find many organisms that are completely undescribed in the science community and are only known by their DNA sequences. We don’t yet know what they do, how they eat or how they live.”

By studying these organisms, researchers hope to better understand how these microbes live in such extreme environments.

“There are components of each of the sites that can relate to environments in space,” explained Kruger. “For example, if we are able to sample the water coming out of the holes anaerobically, without letting oxygen influence them, then that’s much more representative of something you might find on Europa (a moon of Jupiter) or an icy world where there is plenty of water, but no oxygen.”

With the completion of an initial phase determining whether the underground environments at Sanford Lab are stable—both microbially and chemically—the team is diving into more technically-driven scientific questions, with implications for life on earth, as well as potential life in space.

“This research informs big-picture questions,” said Kruger. “As a whole, we are gaining a better understanding of subsurface microbiology.”

Learn more about DeMMO at Sanford Lab.

*This article has been corrected to include the funding structure and leadership of the DeMMO research program.