2024-02-17 15:15:00
(CNN) — Imagine a completely sterile world. Before you is a volcanic landscape, devoid of flora and fauna. Scattered across this gray and black expanse are shallow bodies of water. In each of these natural pools, a precise combination of chemicals and physical conditions is created that could serve as a source of life on our planet.
Some scientists have theorized that the scene might have looked a lot like this, rather than an ocean setting, when life first emerged on Earth about 4 billion years ago, and a study focused on a modern-day lake in the Canadian province of British Columbia offers new support for that idea.
The shallow, salty body of water sitting atop volcanic rock, known as Last Chance Lake, contains clues that carbonate-rich lakes on ancient Earth could have been a “cradle of life,” according to study co-author David Catling. professor of geosciences at the University of Washington. The finding, published in the journal Nature on January 9, could advance scientific understanding of how life began.
“We were able to look for the specific conditions that people use to synthesize the building blocks of life in nature,” Catling said. “We think we have a very promising place for the origin of life.”
British Columbia’s Last Chance Lake, photographed here during the rainy season in June 2022, contains the highest levels of concentrated phosphate ever recorded in any natural body of water on Earth. (David C. Catling)
Catling and his colleagues first became aware of the lake as a place to focus their research after a literature review unearthed an unpublished master’s thesis from the 1990s that had recorded unusually high levels of phosphate there. But the researchers had to see it for themselves.
last chance lake
Last Chance Lake is no more than 30 centimeters deep. Located on a volcanic plateau in British Columbia more than 1,000 meters (3,280 feet) above sea level, it contains the highest concentrated levels of phosphate ever recorded in any natural body of water on Earth.
Haas shows a piece of dry season lake crust taken from Last Chance Lake in September 2022. The researchers used the lake as an “analog environment” to understand soda lakes on the early Earth. (David C. Catling)
A critical component of biological molecules, phosphate is a chemical compound that contains phosphorus, the element that sustains life. It is found in molecules such as RNA and DNA, as well as ATP, a molecule necessary for energy production in all forms of life. The abundance of phosphate in Last Chance Lake is more than 1,000 times greater than that typical of oceans or lakes, according to Sebastian Haas, a postdoctoral researcher who studies the microbiology and chemistry of aquatic environments at the University of Washington, who led the paper. .
Between 2021 and 2022, the team of researchers visited Last Chance Lake to collect and analyze water and sediment samples.
That’s when they discovered that Last Chance Lake is not only a hotbed for phosphate, but also for the mineral dolomite, which allows phosphorus to accumulate in this environment and was formed in response to a reaction in the lake between calcium, magnesium and carbonate. Composite chemical processes, influenced by minerals in the volcanic rock on which the lake formed, as well as an arid climate, effectively produced unique concentrations of phosphate, a set of conditions that researchers believe may have once led to the emergence of life on Earth, according to Haas.
“We are adding credibility to the idea that this type of environment would be favorable for the origin of life, and it is plausible,” he said.
Last Chance Lake is not 4 billion years old, in fact it is estimated to be less than 10,000 years old. The site is simply a modern analogy, or a natural snapshot of the past that ultimately offers scientists the opportunity to better understand what the primordial Earth may have been like outside of a laboratory.
“There is every reason to believe that similar lakes would have existed on the first Earth about 4 billion years ago, because the volcanic rocks on which Last Chance Lake sits are basically a prerequisite for the formation of soda lakes,” he said. Haas. “And what we’re partially showing here is that soda lake water chemistry is the prerequisite for these high phosphate levels.”
Darwin’s warm little ponds
“Soda lakes,” like Last Chance Lake, are shallow bodies of water riddled with dissolved sodium and carbonate, much like baking soda, which typically come from interactions between water and volcanic rocks. They can be found all over the world, but are much less common than other saline bodies of water.
“These types of lakes have the highest levels of phosphate that match what people use in the lab to make (genetic molecules),” Catling said.
When scientists attempted in a laboratory to replicate the chemical reactions that make biomolecules key to the origin of life, the phosphate concentrations needed were up to a million times higher than those normally found in natural bodies of water. of the world.
“If you had these types of lakes on ancient Earth, they would have very high phosphate content, just like Last Chance Lake,” Catling added.
Bodies of water like these have long been on scientists’ radar as potential sources of primordial life. In the 19th century, Charles Darwin first wrote about his “warm little pond” theory, which proposed that warm, shallow, phosphate-rich lakes could have been where the first molecules of life formed.
“Part of what (Darwin) imagines are these bubbling ponds … like Yellowstone,” said Matthew Pasek, a professor at the University of South Florida who studies the chemistry of phosphorus and the origins of biological sciences.
But this isn’t the only popular theory about how life first appeared on Earth billions of years ago. Another is that life began in hydrothermal vents in the deep sea.
The new study adds to the body of evidence supporting the warm little pond hypothesis, according to Pasek, who was not involved in the research.
“The main point, that you can have such high concentrations of phosphate in these ponds, is definitely reinforced by this finding,” he said. “And it shows, ‘This is how that can happen.'”
Still, phosphate in massive abundance is not the only substance necessary for the origin of life. That list of prerequisites also includes carbon and nitrogen sources, as well as the appropriate chemical and physical elements (including phenomena known as wet-dry cycles) that allow the formation of the necessary chemical compounds and reactions.
But the authors said they are not arguing that today’s Last Chance Lake has all the components needed for the building blocks of life, just that it contains some essential pieces.
“The current Last Chance Lake does not contain several chemicals that we now believe are likely crucial to the origin of life,” Haas said, citing cyanide as an example. Previous studies suggest that a primordial version of soda lake may well have included the substance.
While this work “does not uniquely resolve the question of where life originated,” according to Woodward Fischer, a geobiologist at the California Institute of Technology who was not involved in the study, “it highlights current environments on Earth’s surface that “Scientists can study in greater detail to better understand the mechanisms responsible for the establishment of life on our planet and potentially elsewhere.”
The origin of life on Earth and beyond
If life really arose in soda lakes on land, rather than at the bottom of the ocean, that knowledge could, in theory, aid the search for evidence of life beyond Earth.
“If you thought life originated at the bottom of the ocean, you could take a closer look at the subglacial ocean on the moons of Saturn and Jupiter,” Haas said. “But if you think that life originated on Earth’s land surface, planets like Mars could be much more important.”
The same type of rock formation that produces soda lakes can be found on much of the surface of rocky planets like Mars, suggesting that life may have formed similarly elsewhere in the universe.
“Understanding how life originated on Earth has this importance for our search for life beyond Earth,” Haas told CNN. “Better understanding how life originated on Earth allows us to search for life on other planets, or moons of other planets, in the solar system.”
Ayurella Horn-Muller has reported for Axios and Climate Central. Her book, “Devoured: The Extraordinary Story of Kudzu, the Vine That Ate the South,” will be out in the spring.
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