How soda lakes may have sparked life on Earth

Phosphorus, alongside nitrogen and carbon, is an essential element for life on Earth – integral to molecules like DNA, RNA, and ATP. 

Yet despite its importance, phosphorus is relatively scarce at Earth’s surface, posing a long-standing question: how did living organisms first acquire enough phosphorus to jumpstart the biochemical processes necessary for life?

A new study, led by Craig Walton from ETH Zurich, offers a novel explanation. His work points to large, landlocked “soda lakes” as potential reservoirs that could have maintained sufficiently high concentrations of phosphorus to support prebiotic chemistry and eventually nurture early life. 

Why phosphorus is essential – yet scarce

Phosphorus shapes all life on Earth: it helps form the backbone of DNA and RNA, carries energy in cells through ATP, and is a key ingredient in many other biochemical reactions. However, unlike nitrogen and carbon, phosphorus is in limited supply. 

Experiments in labs have shown that prebiotic chemistry – chemical reactions that likely preceded life – requires phosphorus levels roughly 10,000 times higher than what typically exists in natural waters.

This shortfall raises the question: how did Earth’s early environment ever manage to concentrate enough phosphorus for the formation of life?

Soda lakes as phosphorus hotspots

Walton posits that large soda lakes – those without natural runoff – could have built and sustained extremely high concentrations of phosphorus. 

Because water in these lakes escapes primarily via evaporation, phosphorus remains in the lake instead of being washed away by streams or rivers. Over time, the concentration of phosphorus can climb dramatically.

The concept of soda lakes as potential cradles of life is not entirely new; researchers at the University of Washington proposed something similar in 2020. 

But Walton’s research adds detail to this hypothesis, suggesting that only relatively large soda lakes would have had the right conditions – namely, a steady and abundant supply of phosphorus via inflowing water, coupled with minimal outflow – to maintain levels high enough for both prebiotic chemistry and newly emerged life forms.

Smaller lakes, by contrast, might experience sudden drops in phosphorus as soon as life starts to consume it, thereby stifling chemical reactions and halting further biological development. 

Large soda lakes, however, can absorb that consumption thanks to ongoing inputs from tributaries or other sources, keeping phosphorus concentrations robust over longer timeframes.

Implications for life’s beginnings

One real-world illustration of a suitable soda lake is Mono Lake in California. About twice the size of Lake Zurich, Mono Lake consistently supports diverse life due to its high phosphorus concentration. 

Walton’s findings suggest that a lake of comparable size on the early Earth, fed by rivers and left to evaporate, could have sustained similar or even higher phosphorus levels, driving the chemical processes integral to the formation of life.

Walton’s theory indicates that the origin of life might have been more likely in large bodies of water than in the “small warm pond” that Charles Darwin once imagined. 

In the unique environment of a large soda lake, not only would the necessary phosphorus be plentiful, but geological and ecological dynamics would also remain favorable over extended periods. This would give emergent life enough breathing room to evolve without quickly depleting its essential resources.

“This new theory helps to solve another piece of the puzzle of the origin of life on Earth,” Walton said. Because soda lakes can trap water, minerals, and key elements like phosphorus more effectively than smaller ponds, they may have fostered the right balance of chemical conditions and resources that early life-forms needed.

Soda lakes and prebiotic chemistry 

While many questions remain about how life first formed on Earth, Walton’s findings offer a compelling argument that large soda lakes, with their high phosphorus retention, could have provided an ideal setting for prebiotic chemistry. 

If further research reinforces these conclusions, the longstanding puzzle about how Earth’s earliest life managed to obtain enough phosphorus for complex biochemical processes may take another step toward resolution.

By tying the early chemical environment to known geological settings, these insights open fresh avenues for investigating life’s origins – both on our planet and, potentially, on alien worlds that might host similar lake conditions.

The study is published in the journal Science Advances.

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