One of the main chemical elements of life is phosphorus, forming the backbone of DNA and RNA particles, acting as the primary resource for energy in all cells, and fixing the lipids that divide cells from their enclosing settings.
Scientists have pondered for eons how did a lifeless setting on the early Earth provided this main element in creating life.
“For 50 years, what’s called ‘the phosphate problem’ has plagued studies on the origin of life,” said senior author Jonathan Toner, a University of Washington research assistant professor of Earth and space sciences.
The issue is chemical responses that make the DNA of organisms require a large amount of phosphorus, but this element is rather scarce. New research from the University of Washington, published on December 30th, 2019 in the journal Proceedings of the National Academy of Sciences, says it found an answer to this question in specific types of lakes.
Origins of Life
The paper concentrates on lakes abounding of carbonate, which take shape in dry settings within depressions that carry water draining from the encircling landscape. Due to the high evaporation rates, the lake waters centralizes into salty and alkaline resources.
Such lakes also called alkaline or soda lakes, have formed on all seven continents. The scientists first analyzed phosphorus calculations in existing lakes rich in carbonates, such as Mono Lake in California, Lake Magadi in Kenya, and Lonar Lake in India.
Even though the precise concentration depends on where the swatches were acquired from and during what season, the team of scientists discovered the fact that lakes rich in carbonate have up to 50,000 times more phosphorus levels in the seawater, rivers, and other kinds of lakes. Such high densities indicate the existence of some kind of usual, natural system that makes phosphorus gather in these water bodies.
At the moment, these lakes abounding in carbonate are biologically rich and support life, spanning from microbes to flocks of flamingoes. These organisms have an impact on the lake’s chemistry, so researchers experimented in the lab with bottles of water, rich in carbonate at various chemical compositions to see how the lakes get phosphorus, and how the level of phosphorus concentrations could get in an environment that lacked life.
Solving an Ancient Question
The reason behind those high phosphorus levels is due to the waters’ carbonate content. In most lakes, calcium, the most abundant element found on Earth, binds to phosphorus to make solid calcium phosphate minerals, which cannot be accessed by life.
However, in waters rich in carbonate, the carbonate surpasses phosphate to link with calcium, leaving a part of the phosphate unaffected. Laboratory experiments that merged ingredients at various concentrations demonstrate that calcium links to carbonate and leaves the phosphate alone in the water.
“It’s a straightforward idea, which is its appeal,” Toner said. “It solves the phosphate problem in an elegant and plausible way.”
Co-author of the research, David Catling, a University of Washington professor of Earth and space sciences explained:“The extremely high phosphate levels in these lakes and ponds would have driven reactions that put phosphorus into the molecular building blocks of RNA, proteins, and fats, all of which were needed to get life going.”
The carbon dioxide-abundant air on the early Earth, about four billion years ago, would have been perfect for producing such lakes and enabling them to get a maximum level of phosphorus. Lakes rich in carbonate are prone to form in atmospheres with high levels of carbon dioxide. Moreover, dioxide evaporates in water to create acid environments that effectively generate phosphorus from rocks.
“The early Earth was a volcanically active place, so you would have had lots of fresh volcanic rock reacting with carbon dioxide and supplying carbonate and phosphorus to lakes,” Toner said. “The early Earth could have hosted many carbonate-rich lakes, which would have had high enough phosphorus concentrations to get life started.”