Life on Earth may have first sparked in shallow "soda lakes"

The concept of life’s emergence in a “warm little pond,” as postulated by Charles Darwin, has fascinated scientists for generations. An intriguing study from the University of Washington reexamines this theory that life on Earth evolved in shallow soda lakes.

Researchers have found that soda lakes, particularly a shallow one in western Canada, may provide the perfect conditions for the birth of life, a hypothesis that reimagines our understanding of life’s origins on Earth about 4 billion years ago.

Tracing life’s molecular origins

The journey to this discovery began with the acknowledgment that life’s complex molecules can spontaneously form under specific conditions.

This notion, dramatized in the popular film “Lessons in Chemistry,” is rooted in the real-life breakthroughs of the 1950s and beyond.

These advancements revealed the spontaneous formation of amino acids and, later, the building blocks of RNA. However, a significant hurdle, known as the “phosphate problem,” stood in the way.

The emergence of life requires high phosphate concentrations, far exceeding those found in natural water bodies like rivers, lakes, or oceans.

“I think these soda lakes provide an answer to the phosphate problem,” said senior author David Catling, a UW professor of Earth and space sciences.

“Our answer is hopeful: This environment should occur on the early Earth, and probably on other planets, because it’s just a natural outcome of the way that planetary surfaces are made and how water chemistry works,” Catling explained.

Why soda lakes are unique

These lakes are unique due to their high levels of dissolved sodium and carbonate, akin to baking soda, resulting from interactions between water and volcanic rocks.

Moreover, they can contain elevated phosphate levels, potentially solving the puzzle of life’s emergence.

In 2019, University of Washington researchers had theorized that soda lakes could naturally concentrate phosphate to levels a million times higher than typical waters.

Their latest study aimed to confirm this in a real-world setting, leading them to Last Chance Lake in British Columbia, Canada.

This shallow, murky lake, situated on federal land, rests above volcanic rock and experiences conditions ideal for a soda lake: low water levels and high compound concentration due to evaporation.

Cradles of life on Earth and other planets

The team’s analysis, as published in their recent paper, suggests that soda lakes could indeed be cradles for the emergence of life on Earth and potentially on other planets.

“We studied a natural environment that should be common throughout the solar system. Volcanic rocks are prevalent on the surfaces of planets, so this same water chemistry could have occurred not just on early Earth, but also on early Mars and early Venus, if liquid water was present,” said lead author Sebastian Haas, a UW postdoctoral researcher in Earth and space sciences.

Volcanic rock prevalence on planetary surfaces suggests that similar chemical processes could have occurred on early Mars and Venus, given the presence of liquid water.

The research team visited Last Chance Lake three times in 2021-2022, collecting samples of water, lake sediment, and salt crust to understand its unique chemistry.

In most lakes, phosphate binds with calcium to form insoluble calcium phosphate. However, in Last Chance Lake, calcium combines with carbonate and magnesium to form dolomite, leaving phosphate in high concentration in the water.

“You have this seemingly dry salt flat, but there are nooks and crannies. And between the salt and the sediment there are little pockets of water that are really high in dissolved phosphate,” Haas said.

“What we wanted to understand was why and when could this happen on the ancient Earth, in order to provide a cradle for the origin of life.”

A tale of two soda lakes

Interestingly, the study also compared Last Chance Lake with nearby Goodenough Lake to understand why life hadn’t consumed the high phosphate levels in Last Chance Lake.

The findings revealed that the saltiness of Last Chance Lake inhibited lifeforms that fix nitrogen, unlike in Goodenough Lake, which supports life that consumes phosphate.

“This study adds to growing evidence that evaporative soda lakes are environments meeting the requirements for origin-of-life chemistry by accumulating key ingredients at high concentrations,” Catling said.

This characteristic makes Last Chance Lake a more accurate representation of a lifeless early Earth environment.

Professor Catling emphasizes the broader implications of this research for understanding life’s origins.

“These new findings will help inform origin-of-life researchers who are either replicating these reactions in the lab or are looking for potentially habitable environments on other planets,” Catling concluded.

In summary, the University of Washington’s study on soda lakes, particularly Last Chance Lake, opens a fascinating window into the past, offering a plausible answer to the long-standing question of how life might have emerged on our planet and possibly others.

This discovery not only enriches our understanding of life’s origins but also expands the horizons of our search for life beyond Earth.

The full study was published in the journal Communications Earth & Environment.

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