Yellowstone’s treasures may hold clues to life

It’s the most intriguing question facing mankind: What are the origins of life? But addressing this question is getting Michael Gonsior into some hot water.

Gonsior is a tenured associate professor of biogeochemistry at the University of Maryland’s Center for Environmental Science. He studies dissolved organic materials (DOM) from an environment that scientists believe replicates many of the conditions of ancient Earth ― the majestic hot springs in Wyoming’s Yellowstone National Park.

That DOM from those springs could hold clues as to what types of organic matter can exist in environments deep below the earth, where magma and high pressures raise water temperatures to about 350 degrees Celsius. The extreme environments of hot springs are thought to be the closest still existing windows into conditions that might have existed during early Earth.

Yellowstone is home to hundreds of hot springs. Many terminate at ground level, so surface runoff and possible groundwater intrusion adds modern DOM that contaminates possible ancient DOM signatures. But others, called cone springs, protrude above the ground and transport less tainted samples of materials from far below the surface.

Yellowstone’s DOM (YDOM), emanating from the hot springs are unique and show unmatched chemodiversity, which is a term used in analogy to biodiversity but describe the chemical complexity of organic molecules.

The hot springs are classified into four main types: alkaline-chloride, mixed alkaline-chloride, acid-chloride-sulfate and travertine-precipitating. Fluorescence spectroscopy, used alongside other methods, show clearly, through excitation emission matrix (EEM) molecular signatures, unique features in Yellowstone’s springs. In fact, ultrahigh resolution mass spectrometry confirmed that YDOM contains thousands of molecular formulas unique to Yellowstone’s hot springs.

“There are some springs and specifically those that more directly tap the hydrothermal source which are the clear alkaline-chloride or Alkaline Springs that have a unique, low wavelengths fluorescence, which is quite surprising,” Gonsior said. “And we don't know what those compounds are yet that are forming these fluorescence signals. It remains a mystery at the moment.”

Among the hot springs are the park’s celebrated geysers. These also contain hydrothermally heated liquids but travel through constricted pathways to the surface, causing these to occasionally erupt and release built-up pressure. The park is a geological anomaly. Yellowstone is home to 60 percent of the world's geysers and hot springs, including its best known geyser, Old Faithful.

Oxygen is absent deep in the aquifer or the hot springs system. That with the heat and pressure creates what scientists call reduced environments.

“If you don't have oxygen there, then you can maintain organics, which would otherwise be quite quickly oxidized,” he said. “This is why (the springs) have been used as an analog to early Earth or Hadean Earth, before there was oxygen on the planet.”

Hadean Earth began with the formation of the Earth about 4.6 billion years ago and ended 4 billion years ago, according to the International Commission on Stratigraphy.

Gonsior’s team characterizes Yellowstone’s YDOMs using EEM fluorescence, nuclear magnetic resonance, and ultrahigh resolution mass spectra.

Gonsior measures EEM’s with HORIBA’s Aqualog® spectrofluorometer, which utilizes proprietary A-TEEM technology (absorbance-transmittance fluorescence Excitation Emission Matrix) spectroscopy. The technique simultaneously measure both absorbance spectra and fluorescence EEMs, which are acquired 100 times faster than other instruments, allowing more samples to be analyzed in a shorter period of time.

The researchers obtained EEM molecular signatures recently with methanolic YDOM and aquatic SPE-DOM (Solid phase extraction) samples, dried under ultrapure nitrogen and then re-dissolved in ultrapure water. They measured EEM spectra at excitation wavelengths ranging from 230–500 nm and emission wavelengths between 200–600 nm. The recorded EEM spectra were then corrected for inner filtering effect automatically through A-TEEM, Raleigh and Raman scattering, , and normalized to a 1 ppm quinine sulfate standard and expressed in quinine sulfate units (QSU).

The hot springs offer researchers another rare opportunity. Normal bacteria cannot survive the near boiling temperature of the springs, so none of the bacteria typically found in freshwater exist in the near boiling hot springs. That means the only organisms in those hot springs are extremophiles ― extreme organisms ― or a subcategory called thermophiles that thrive at relatively high temperatures between 41 and 122 Celsius.

Thermophiles are significant for programs like exobiology, because in ancient Earth, life had to form under extreme chemical, temperature and pressure conditions without oxygen. Understanding how life can be and exist in absolutely extreme conditions like boiling temperatures and various acidic environments might advance our insight into the origins of life on Earth.

It’s even been theorized that these extremophiles could maybe be related to those first organisms, which evolved on earth.

“Life obviously needed some organic precursors and whatever mechanism was behind it,” Gonsior said. “This is still one of the most intriguing questions, where we're looking into is the origin of life. There are a lot of reasonably new theories with interaction of organics, with mineral faces and actually interesting redox (oxidation-reduction) reactions, which do occur under specific conditions repeatedly. There are a lot of ideas about how it could have happened, but we still don't know what existed.”

Gonsior believes if researchers learn that some of the old signatures contained in YDOM might actually only exist under extreme chemical conditions ― which rarely exist anymore on earth before the world got oxygenated ― it could lead to clues to the formation of life.

And it could have implications beyond the planet Earth.

“All of these things are pretty much unknown today, but it is very important, because we are now discovering very diverse, organic matter in meteorites and, and other extraterrestrial sources like those return missions going on right now where they're taking samples from actual asteroids.” In particular, the work by Professor Schmitt-Kopplin and colleagues on organic matter in meteorites have been ground breaking.

These are the interesting parts to see what's going on when you have ancient life, and examine the extraterrestrial organic matter to see if there's any comparison,” he said. “Because we're still trying to understand the history of our Earth and how life emerged in the first place. So this is also really a question, what was there at the beginning right before life emerged. And, and maybe that is the window into the past, but we don't know yet. So it would be interesting to really learn much more about that uniqueness of that organic matter present in Yellowstone hot springs and other geothermal area.”

Yellowstone is a difficult place to conduct research. Scientists are squeezed between avoiding the mild weather of high tourism seasons and the harsh conditions of Wyoming winters at high altitude.

“We usually targeted early fall before it starts snowing,” Gonsior said. “The first time we sampled the temperature dropped to minus 16 in the morning. But most of the time it's still nice and the park is very pretty in fall with active wildlife abound. Sometime we have to share our springs with bison, so a safe distance is essential. It depends on the year because the park is at higher elevation. The plateau is probably about 8,000 feet high, but of course that depends on where you are in the park. So the weather can change quickly.”

The researchers hike to sites over hilly terrain and have worked on camp sites to reach remote hot springs off the beaten path more easily. They must sample large volumes of water, sometimes 20 liters. The conditions pose obstacles.

“We have to carry the water in glass bottles because they're boiling hot,” he said. “You have to be careful that the glass doesn't break when you pour boiling water into it, especially when it is cold. And then you have to carry them out.”

The jars weigh about 50 pounds filled, and it can be tiring to carry them for a few miles. The team uses backpacks, but initially the water is too hot to carry, so they must let the water is cool before transporting the samples to the trailer, where some analytical equipment is used to make initial measurements.

The grandeur of Yellowstone is a long way from Gonsior’s roots. He grew up in a small German village close to the Dutch border. As a first generation university student, the planet’s natural systems intrigued him. That despite being surrounded by open pit lignite mining, in the coal mining town of Hueckelhoven.

Gonsior did his undergraduate and master’s studies in Germany, with some time abroad in Scotland, Canada and Ecuador. He earned his Ph.D. in New Zealand, before doing a post-doctoral work at the University of California, Irvine. A half-year of humanitarian work in Kenya followed, as did more post-doc research in Sweden, before moving back to the U.S. in 2012 at his current position.

Gonsior’s long term research goal is to better understand the sources of Yellowstone’s organic matter to get a better idea what might have existed on early Earth. And then to understand what reactivity is involved in transforming organic matter under these extreme conditions.

But in light of the issues the world faces, what benefits will understanding how life formed provide us? Are there practical applications to this knowledge?

Gonsior shot back.

“This is always a chicken and egg question,” he said. “With any fundamental research, it's reasonably difficult to predict what that will be in particular. Fundamental research will trigger applied research later down the track, but if you haven't been down that road, but you might not know what that trail is going to be.”

For example, when Thomas Brock discovered microorganisms in the boiling hot springs in Yellowstone, who would have thought that Yellowstone thermophilic bacteria and the development of the Polymerase Chain Reaction (PCR) method would revolutionize medical science. To date, this technique is arguably the most used tool in microbiological and medical applied research. We have learned a tremendous amount about results obtained from basic research in Yellowstone hot springs, which have fundamentally shaped the well-being of human kind. For example, none of the research to find a cure for Covid-19 would be even possible without the initial fundamental research undertaken by the research team led by Prof. Thomas Brock in the late 1960s.

In other words, the applications from an answer to the question of the origins of life will define itself.

“If you can really determine what the mechanisms are, we can make prediction how that might happen in other systems as well, outside of Earth.”

“If you only do applied research because you already have an idea of what you're doing, that means you're never looking back and you never make that accidental discovery, which is purely based on connecting the dots. It’s about pushing the boundaries of science.”

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