Discoveries may alter scientists’ perceptions of the environments in which life originally originated.
Seawater may have provided the phosphorus necessary for emergent life.
Researchers from the universities of Cambridge and Cape Town may have solved the mystery of how phosphorus became an essential component of life on Earth by recreating prehistoric seawater containing the element in a lab .
Their findings, published in the journal Nature Communicationsuggest that seawater could be the missing source of phosphate, suggesting that it could have been present in sufficient quantities to sustain life without the need for special environmental conditions.
“It could really change the way we think about the environments in which life originated,” said Professor Nick Tosca from the University of Cambridge, who was one of the study’s authors.
The research, led by University of Cambridge Ph.D. student Matthew Brady, finds that seawater in the early years could contain 1,000 to 10,000 times more phosphate than previously thought, provided that the water contains a lot of iron.
Phosphate is an essential element of DNA and RNA, which are the building blocks of life, despite being one of the least common elements in the universe relative to its biological significance. Phosphate is also relatively inaccessible in its mineral form – it can be difficult to dissolve in water for life to use.
Scientists have long suspected that phosphorus is part of biology from the start, but they have only recently begun to recognize phosphate’s role in directing the synthesis of molecules necessary for life on Earth. biomolecules if there’s a lot of phosphate in solution,” said Tosca, professor of mineralogy and petrology in Cambridge’s Department of Earth Sciences.
However, there has been some debate over the precise circumstances required to create phosphate. According to some research, phosphate should actually be even less accessible to life when iron is abundant. However, this is disputed as early Earth’s atmosphere was low in oxygen and iron would have been widespread.
They used geochemical modeling to simulate early Earth conditions to understand how life came to depend on phosphate and the type of environment in which this element would have evolved.
“It’s exciting to see how simple experiments in a bottle can disrupt our thinking about the conditions that were present on early Earth,” Brady said.
In the lab, they made seawater with the same chemistry that was thought to have existed early in Earth’s history. They also conducted their experiments in an oxygen-deprived atmosphere, just like on ancient Earth.
The team’s results suggest that seawater itself could have been a major source of this essential element.
“This doesn’t necessarily mean that life on Earth began in seawater,” Tosca said, “it opens up a lot of possibilities for how seawater could have provided phosphate to different environments – for example, lakes, lagoons or shores where sea spray could have transported phosphate to land.
Previously, scientists had proposed a range of ways to generate phosphate, with some theories involving special environments such as acidic volcanic springs or alkaline lakes, and rare minerals found only in meteorites.
“We had a hunch that iron was the key to phosphate solubility, but there just wasn’t enough data,” Tosca said. The idea for the team’s experiments came when they examined the waters that bathe the sediments deposited in the modern Baltic Sea. “It’s unusual because it’s high in phosphate and iron – we started to wonder what was so different about those particular waters.”
In their experiments, the researchers added different amounts of iron to a range of synthetic seawater samples and tested how much phosphorus it could hold before crystals formed and the minerals separated from the liquid. They then incorporated these data points into a model that could predict how much phosphate ancient seawater might contain.
The pore waters of the Baltic Sea provided a set of modern samples with which they tested their model. “We could replicate this unusual water chemistry perfectly,” Tosca said. From there, they continued to explore seawater chemistry before any biology.
The findings also have implications for scientists trying to understand the possibilities of life beyond Earth. “If iron helps put more phosphate into solution, that might be relevant for early " data-gt-translate-attributes="[{" attribute="">March“, said Tosca.
Evidence of water on ancient Mars is abundant, including ancient riverbeds and flood deposits, and we also know that there was a lot of iron on the surface and the atmosphere was sometimes low in oxygen, Tosca said.
Their simulations of surface water filtering through rocks on the Martian surface suggest that iron-rich water may have provided phosphates in this environment as well.
“It’s going to be fascinating to see how the community uses our findings to explore new, alternative pathways for the evolution of life on our planet and beyond,” Brady said.
Reference: “Marine Phosphate Availability and the Chemical Origins of Life on Earth” by Matthew P. Brady, Rosalie Tostevin and Nicholas J. Tosca, September 2, 2022, Nature Communication.
DOI: 10.1038/s41467-022-32815-x
Comments are closed.