How Yellowstone’s Earthquakes may Illuminate Life on Other Planets

Believe you and I sing
Tiny and wise and could if we had to
Eat stone and go on
– Richard Hugo’s gravestone epitaph from his poem, Glen Uig

An old cartoon taped to many a scientist’s office door shows a blackboard covered in equations, with a note in the middle reading, “And then a miracle occurs.”

That was how Eric Boyd felt when he checked the sensors on a microbiology project next to Yellowstone Lake and realized a rare seismic event had exposed a secret of ancient life.

“To capture an earthquake swarm happening right next door under the lake, you’ve got to be extremely lucky,” the Montana State University microbiologist told Mountain Journal. “Timing an earthquake is impossible. There’s no way you’d get the National Science Foundation to fund this work if that’s part of the plan.”

Boyd’s research explores how Earth’s earliest lifeforms found food. He starts from the hypothesis that the planet’s first lifeforms appeared about 3.8 billion years ago, before there was an atmosphere to block destructive solar radiation. So instead of attempting to survive on the surface like much of modern life, those original organisms evolved underground.

And rather than breathing oxygen, they consumed sulfur and hydrogen, which they could process out of surrounding minerals. The question was: How does a microbe find its next meal when it’s fixed to an immobile rock?

Over the past two decades, Boyd has been probing the unique geothermal features of Yellowstone National Park for answers. In 2019, he was setting up what was supposed to be an automated monitoring system for a 100-meter-deep well drilled into a freshwater aquifer near Grant Village. Things were not going well.

“Long story short, it was [during] COVID,” Boyd said. “Nothing got done the way it should have. It was meant to be a seismically triggered pressure meter in the borehole, which would send signals to start sampling. But the person who designed the sampler died. I’m a biologist, not an engineer, so that created a bottleneck.”

With supply chains and communications scrambled by the COVID-19 pandemic, Boyd drove four hours back and forth into the park to take manual samples over the summer. On one of those trips, all the indicators shifted.

“There was a massive change in chemistry of the fluids we were sampling,” he said. “We knew something had changed, we just didn’t know why. Then we looked at the seismic logs, and sure enough we were in the midst of a seismic swarm. That was the ‘aha’ moment.”

Yellowstone Park records about 3,000 earthquakes a year. Some come in “swarms,” the term for several small quakes in a specific area over a short time. As important as they are to Yellowstone’s natural history, seismic activity’s unpredictability remains a formidable research obstacle. No one knows when or where the next one will hit.  

We do know that inert minerals can change form when surrounding conditions change — think of a shiny nail turning rusty in a glass of water. Earthquakes fracture rocks, allowing water into new places. That water can transport acidic compounds from Yellowstone’s volcanic vents into the surrounding alkaline mineral structures, resulting in chemical reactions releasing sulfur and hydrogen. We notice the process as the rotten-egg smell wafting around many of the park’s thermal features.

That’s the abiotic, or nonliving, version of change. But those cracked rocks and flowing waters can also serve as the ancient-earth version of DoorDash, delivering nutrients that rock-locked microbes can turn into food. Coincidently, their digestion process also gives off the hydrogen sulfide stink.

“There’s one deep, parent aquifer feeding all the alkaline systems in the park,” Boyd said. “And when it’s mixing with near-surface waters, that’s when you get acidic hot springs like Norris or Mud Volcano. Microbes might accelerate that reaction.”

As one might expect, the chemistry of the water returned to normal on Boyd’s next sample test. That might seem like a confirmation of the obvious: give a creature food and it consumes the offering. But that basic science has also helped explain the wider nature of Yellowstone’s underground systems, as explained in “Seismic Shifts in the Geochemical and Microbial Composition of a Yellowstone Aquifer,” on which he was lead author.

“Eric’s investigation into how seismic activity shapes microbial communities in the Yellowstone ecosystem is yet another excellent example of his groundbreaking research exploring how microbial life persists and evolves in extreme environments,” said Jovanka Voyich, head of the Department of Microbiology and Cell Biology, which is housed in MSU’s College of Agriculture. “The fact that MSU undergraduate and graduate students can take courses and receive mentorship from one of the world’s most prestigious geobiologists is a remarkable educational opportunity.”

And recording that rise and fall of microbial activity during a seismic event could help identify life on other worlds. For example, seismographs placed on Mars have recently confirmed the planet has “marsquakes” (earthquakes happen only on Earth).

“Mars doesn’t have an ozone layer, so its surface radiation levels are extremely high,” Boyd said. “Any existing life is probably subsurface. NASA wants to know what processes support life in these places. If seismic activity has this kind of subsurface influence on Earth, it may help sustain life on other planets.”

Yellowstone offers an ideal place to learn about microbes because its extreme conditions — super-hot water, earthquakes, radical weather shifts and a relatively intact ecosystem — provide examples hard to find anywhere else. As recounted in Bozeman author David Quammen’s The Tangled Tree, research on the Thermus aquaticus microbe in Yellowstone’s Octopus Spring helped unlock CRISPR gene-editing techniques for DNA analysis. Microbial life processes produce the soil that other plants and animals depend on, as well as the nutrients that hold together food webs. Boyd summarizes the situation: “Eliminate microbes, you eliminate higher forms of life.”

Invisible to us, microbes nevertheless make up almost one-third of the biomass of the planet. They can live for thousands of years, lying dormant until a slug of food comes along. The challenge is knowing where to look and then being there when something happens.

Gambling expert John Scarne wrote about watching a dice player win 39 consecutive passes: an accomplishment so unusual the odds are 956,211,843,725 to 1 against it happening. But when he factored in the billions of dice games played around the world he reconsidered. “I was thunderstruck,” he wrote in his classic Scarne’s Complete Guide to Gambling, “not because the world record was established, but because I was on hand to witness it. The odds against that are many times greater.”

“Nobody’s sampled during an earthquake storm and after,” Boyd said. “That’s the fortunate bit. We just wanted a preliminary glimpse, and we happened to nail things.”