Scientists have discovered a lake that might be a good match for Darwin’s “warm little ponds”, the place where life began on primitive Earth.
A team of scientists from the University of Washington made the discovery when they found a shallow “soda lake” in Western Canada that appeared to have the chemistry and conditions a small body of water would need to facilitate the spontaneous synthesis of complex molecules. It gave rise to life on Earth approximately 4 billion years ago.
Soda lakes, such as the one this research focuses on, are small bodies of water that contain high levels of dissolved carbonate and sodium; This is like putting a large amount of baking soda in them. However, in this case, the high levels of dissolved sodium and carbonate result from reactions between water and volcanic rocks.
The findings could help solve a long-standing problem in explaining how life on Earth arose and could also be applied to other planets in the solar system, such as Mars and Venus.
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Since the 1950s, researchers have succeeded in obtaining biological molecules such as amino acids and the building blocks of RNA from inorganic molecules, but there has been a long-standing problem in the next step of this process. Along with RNA and DNA, the key molecules of life, the membranes of living cells require a backbone composed of naturally occurring molecules of the element phosphorus, known as phosphate.
The concentrations of phosphate required to create biomolecules in the laboratory are 1 million times higher than levels normally found in rivers, lakes or oceans. This has become known as the “phosphate problem” in theories about the emergence of life on Earth, and this new research suggests soda lakes could be the solution.
“I think these soda lakes provide an answer to the phosphate problem,” David Catling, senior author of the study and professor of Earth and space sciences at the University of Washington, said in a statement. “Our answer is promising: This environment must have formed on early Earth, and possibly on other planets as well, because it is a natural consequence of the way planetary surfaces are formed and how water chemistry works.”
Why are soda lakes potential cradles for life?
Soda lakes contain large amounts of phosphate as well as high levels of dissolved carbonate and sodium; A 2019 study found that concentrations of these molecules in these small bodies of water can be up to 1 million times higher than those found in typical bodies of water. This. This means that soda lakes could be ideal places for the basic molecules of life to emerge.
To test this, the University of Washington set out to study just such a soda lake, settling on Last Chance Lake, a 1-meter-deep (30 cm) dark lake located at the end of a dirt road on the Cariboo Plateau in British Columbia. , Canada. This particular soda lake was determined to have the highest known phosphate level in the 1990s.
In addition to having volcanic basalt rock at the bottom of Last Chance Lake, it also has a dry, windy climate that keeps water levels low and rapidly evaporates incoming water, concentrating dissolved compounds.
The scientists behind this new research visited the lake three times between 2021 and 2022, when it was frozen in both summer and winter.
“You have a seemingly dry salt flat, but there are nooks and crannies. Between the salt and the sediment, there are little pockets of water that are really high in dissolved phosphate,” said team member and University of Washington postdoctoral researcher Sebastian Haas. . “What we wanted to understand was why and when this might have happened on ancient Earth to provide a cradle for the origin of life.”
After examining samples of water, lake sediment, and salt crust found in Last Chance Lake to understand the lake’s chemistry, the team found that calcium combines with abundant carbonate and magnesium to form dolomite.
This is different from the situation in other lakes, where phosphate often binds with calcium to form calcium phosphate, which forms the enamel of our teeth and insoluble, depleting phosphate levels.
There is abundant free phosphate residue as a result of calcium being trapped in the dolomite in Last Chance Lake; If these conditions had existed in pools of water approximately 4 billion years ago, they would have allowed the essential components of the origin of life chemistry to exist in the requisitely high concentrations.
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Not only did the team find that Last Chance Lake suggested soda lakes were strong candidates for places where life might have begun on Earth, but they also expected conditions in these lakes to be common to other solar system bodies and planets outside the solar system. extrasolar planets or exoplanets.
“We studied a natural environment that should be common throughout the solar system,” Haas said. “Volcanic rocks are common on the surfaces of planets, so the same water chemistry may have formed not only on early Earth but also on early Mars and early Venus if liquid water had been present.”
“These new findings will help inform origins of life researchers who replicate these reactions in the laboratory or search for potentially habitable environments on other planets,” Catling concluded.
The team’s research was published in the journal Nature Communications Earth & Environment.