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Mammoth Hot Springs in Yellowstone National Park. (Credit: CC photo via Wikimedia Commons; https://commons.wikimedia.org/wiki/File:Mammoth_Hot_springs_04.jpg)

On Earth, life thrives in some of the most seemingly inhospitable environments.

Single-celled organisms like bacteria teem in the hot springs of Yellowstone National Park, where temperatures reach nearly 200 degrees Fahrenheit (93 degrees Celsius). Others dwell deep underground or several miles above Earth’s surface in the stratosphere.

For years, scientists in a field called astrobiology have sought out these organisms. They want to know not just how life evolved on Earth, but how it might evolve on other worlds. They investigate moons in our solar system like Europa and Enceladus where vast and salty oceans lie beneath thick layers of ice.

“There have been so many of these extreme niches that astrobiologists have discovered on Earth,” said Tristan Caro, an astrobiologist who earned his doctorate in geological sciences at С���� Boulder in 2024. “They expand what we can imagine as habitable environments.”

Now, a team of students and early-career researchers have in the journal Nature Communications tackling the potential of this out-there field.

Srishti Kashyap kneels in front of a "hyper-alkaline" spring in Oman. (Credit: Srishti Kashyap)

Tristan Caro conducting astrobiology research in the crater of Mt. St. Helens. (Credit: Tristan Caro)

The authors include Caro, Alta Howells, Srishti Kashyap, Catherine Fontana and Sabrina Elkassas and hail from ���� Boulder, the California Institute of Technology, Woods Hole Oceanographic Institution and the Massachusetts Institute of Technology.

This group argues that pursuing astrobiology may bring dual benefits for humanity. The study of astrobiology can help scientists answer some of the biggest questions ever asked, such as: “Are we alone in the universe?” The discipline also inspires new technologies that may one day make life better on Earth, such as cleaner sources of fuel and tools that pull greenhouse gases out of the atmosphere.

“Astrobiology might seem really esoteric, but it’s deeply tied to the search for new technologies and energy sources,” said Catherine Fontana, a co-author of the article and a graduate student in the Department of Geological Sciences at С���� Boulder.

To mark the new publication, she, Caro and their colleagues discuss what gets them excited about astrobiology—from the almost unbelievable things microbes can do to the fascinating chemistry that exists deep under Earth’s crust. They also share advice for students hoping to get into the field.

As an undergraduate, for example, co-author Kashyap double-majored in astronomy and biology. Then she realized the two subjects weren’t as different as she thought.

“I quickly learned that if I wanted to understand how life could be sustained elsewhere in the universe, I needed to step back and think about the processes that sustain life here,” said Kashyap, now a research associate at С���� Boulder and staff scientist at Blue Marble Space Institute of Science.

Microbial ingenuity

For Caro, much of the fun of being an astrobiologist is diving into the world of microbes.

“What really excites me about astrobiology is its focus on what you could call microbial ingenuity, the ways that they have crafted a variety of strategies to survive and thrive in environments that are hostile to larger organisms like us,” said Caro, now a postdoctoral researcher at CalTech.

He noted that scientists employ a DNA synthesis method known as polymerase chain reaction for countless applications, including COVID screenings and ancestry tests. Researchers first discovered the enzyme that is key to this process inside bacteria living in Yellowstone hot springs.

Fontana studies cyanobacteria, a class of single-celled organisms sometimes known as blue-green algae, that have existed on Earth for 3.5 billion years. Roughly 2.4 billion years ago, they played a key role in causing oxygen concentrations in the atmosphere to spike. Those changes paved the way for the rise of animals, plants and other animals.

Today, researchers are also exploring whether these microbes can become tiny factories—churning out biofuels, biocements and biodegradable plastics.

Elkassas, a co-author the article, explores methanotrophs, microbes that get their energy from methane gas. These microbes live in underground fluids below mud volcanoes in the Pacific Ocean and may absorb large volumes of methane from this environment. ��

Methane is a potent greenhouse gas and a major contributor to climate change. Some scientists are investigating whether methanotrophs and similar organisms may one day be able to help pull methane from the environment and store it safely underground.

“This research exemplifies the ‘dual approach’ to astrobiology by using studies of extreme environments to better understand carbon sequestration processes on Earth, while simultaneously informing how similar metabolisms might operate on other ocean worlds,” said Elkassas, who recently earned her doctorate from the MIT-Woods Hole Joint Program.

In the dark

Howells, who led the perspectives article, has been on track to become an astrobiologist since she was a kid in Bozeman, Montana. She grew up visiting hot springs in Yellowstone and enjoyed watching science fiction staples like “Star Trek” and “Contact.”

“I remember being 8 years old and explaining to my aunt that life likely originated from the ocean as single cells, so this curiosity was ingrained in me from an early age,” said Howells, a research associate at С���� Boulder and research scientist at Blue Marble.

Today, Howells looks for strange new worlds not in outer space, but deep below Earth’s surface.

Howells studies a process known as serpentinization. Deep underground, she explained, certain iron-rich minerals react with water to produce hydrogen gas. Companies around the world have kicked off a race to see if they can mine that gas to make fuel. When burned, hydrogen gas only releases water and not pollutants like carbon dioxide.

Scientists have also discovered microbes living amid those same minerals—an environment that is dark and completely devoid of oxygen, Kashyap said. Many of those microbes also consume hydrogen gas, making them potential competitors for this valuable resource.

“There is a really massive microbial biosphere that resides in these rocks and fluids in Earth’s subsurface,” said Kashyap, who also studies serpentinizing minerals. “We’re trying to understand how they could be a bane or boon for extracting energy from these systems.”

Anne Sheehan, chair of the Department of Geological Sciences, noted that ���� Boulder has long been a leader in astrobiology research.

“One of С���� Boulder’s major strengths in astrobiology is how we develop and train the next generation of scientists,” she said. “Our students and early-career researchers are leading work that spans geology, biology, chemistry and planetary science in ways that are shaping the field of astrobiology. They continue to amaze us.”

Cold water

The five early career researchers are all eager to see more young scientists join astrobiology.

Because this field explores the unknown, including some of the most remote and inhospitable (at least for humans) environments on Earth, astrobiologists never get bored, they said.

“Astrobiology forces me to keep learning something new,” Kashyap said.

Fontana decided to get into the field after “Googling on a whim” and stumbling across a resource called “.” When talking to students, she borrows an analogy from a friend who’s a competitive swimmer.

“My advice for students is to figure out what you're willing to jump into a cold body of water for at 5 a.m.,” she said. “That is your calling.”