Marine Phosphate and the Chemical Origins of Life

Author: University of Cambridge
Published: 27 Sep 2022 - Updated: 5 Jul 2026
Publication Details: Peer-Reviewed | Research, Study, Analysis

Table of Contents:
Synopsis - Definition - Introduction - Main - FAQ's - Insights, Updates - Related Content

Synopsis: This peer reviewed research, published in the journal Nature Communications, examines how phosphate - an essential building block of DNA, RNA, and cell membranes - may have become widely available to early life through ordinary seawater rather than rare environments. Working with recreated primordial seawater in an oxygen-poor setting, scientists from the University of Cambridge and the University of Cape Town found that iron-rich water could hold one thousand to ten thousand times more phosphate than earlier estimates suggested. The findings carry authority as a laboratory-tested, peer reviewed study, and they hold broad interest for readers curious about the origins of life on Earth and the potential for life on early Mars.*

At a Glance

• 1 - The team's iron-based model also points to phosphate availability on early Mars, where oxygen-poor, iron-rich water once flowed.
• 2 - The research began after scientists noticed unusually high iron and phosphate levels in pore waters of the modern Baltic Sea.
• 3 - Seawater phosphate could have reached lakes, lagoons, and shorelines through sea spray, opening several settings where life's chemistry may have begun.

Topic Definition: Marine Phosphate

Marine phosphate refers to the dissolved phosphate present in seawater, where phosphorus exists chiefly as the phosphate ion bound within ocean water and marine sediments. Phosphate is one of the least abundant elements relative to its biological importance, and in mineral form it can be difficult to dissolve, which historically made it hard to explain how early life obtained enough of it. In marine settings, the amount of phosphate that water can hold depends heavily on its chemistry - particularly its iron content - so iron-rich, oxygen-poor seawater like that of the early Earth can carry far greater quantities. Because phosphate is a core component of DNA, RNA, ATP, and cell membranes, its availability in ancient oceans is central to understanding how the chemical foundations of life first assembled.

Introduction

The problem of how phosphorus became a universal ingredient for life on Earth may have been solved by researchers from the University of Cambridge and the University of Cape Town, who have recreated primordial seawater containing the element in the lab.

Their results, published in the journal Nature Communications, show that seawater might be the missing source of phosphate, meaning that it could have been available on a large enough scale for life without requiring special environmental conditions.

"This could change how we think about the environments in which life first originated," said Professor Nick Tosca from the University of Cambridge, who was one of the authors of the study.

The study, which was led by Matthew Brady, a Ph.D. student from the University of Cambridge, shows that early seawater could have held one thousand to ten thousand times more phosphate than previously estimated - as long as the water contained a lot of iron.

Main Content

Phosphate is an essential ingredient in creating life's building blocks - forming a key component of DNA and RNA - but it is one of the least abundant elements in the cosmos of its biological importance. In its mineral form, phosphate is also relatively inaccessible - it can be hard to dissolve in water so that life can use it.

Scientists have long suspected that phosphorus became part of biology early on. Still, they have only recently begun to recognize the role of phosphate in directing the synthesis of molecules required by life on Earth.

"Experiments show it makes amazing things happen - chemists can synthesize crucial biomolecules if there is a lot of phosphate in solution," said Tosca, Professor of Mineralogy & Petrology at Cambridge's Department of Earth Sciences.

But the exact environment needed to produce phosphate has been a topic of discussion. Some studies have suggested that phosphate should be even less accessible to life when iron is abundant. This is, however, controversial because early Earth would have had an oxygen-poor atmosphere where iron would have been widespread.

To understand how life came to depend on phosphate and the sort of environment in which this element would have formed, they carried out geochemical modeling to recreate early conditions on Earth.

"It's exciting to see how simple experiments in a bottle can overturn our thinking about the conditions that were present on the early Earth," said Brady.

In the lab, they made up seawater with the same chemistry thought to have existed in Earth's early history. They also ran their experiments in an atmosphere starved of oxygen, just like on ancient Earth.

The team's results suggest that seawater could have been a major source of this essential element.

"This doesn't necessarily mean that life on Earth started in seawater," said Tosca, "It opens up a lot of possibilities for how seawater could have supplied phosphate to different environments- for instance, lakes, lagoons, or shorelines where sea spray could have carried the phosphate onto land."

Previously, scientists came up with various ways of generating phosphate, some theories involving unique environments such as acidic volcanic springs or alkaline lakes and rare minerals found only in meteorites.

"We had a hunch that iron was key to phosphate solubility, but there just wasn't enough data," said Tosca. The idea for the team's experiments came when they looked at waters that bathe sediments deposited in the modern Baltic Sea. "It is 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. They tested how much phosphorous it could hold before crystals formed and minerals separated from the liquid. They then built these data points into a model to predict how much ancient phosphate seawater could hold.

The Baltic Sea pore waters provided one set of modern samples they used to test their model.

"We could reproduce that unusual water chemistry perfectly," said Tosca. They went on to explore the chemistry of seawater before any biology was around.

The results also have implications for scientists trying to understand the possibilities for life beyond Earth. "If iron helps put more phosphate in solution, then this could have relevance to early Mars," said Tosca.

Evidence for water on ancient Mars is abundant, including old river beds and flood deposits, and we also know that there was a lot of iron at the surface and the atmosphere was at times oxygen-poor, said Tosca.

Their simulations of surface waters filtering through rocks on the Martian surface suggest that iron-rich water might also have supplied phosphates in this environment.

"It's going to be fascinating to see how the community uses our results to explore new, alternative pathways for the evolution of life on our planet and beyond," said Brady.

Frequently Asked Questions

NOTE: Researched FAQ's by Disabled World (DW)

What is phosphate and why does life need it?

Phosphate is a compound containing the phosphate ion, and it forms an essential part of DNA, RNA, ATP, and cell membranes. Without accessible phosphate, the molecules that store genetic information and power cells could not assemble.

Why was phosphate availability on early Earth considered a problem?

Phosphate is scarce relative to its biological importance and can be hard to dissolve in its mineral form. This made it difficult for researchers to explain how early life obtained the large amounts needed for its chemistry.

How does iron affect how much phosphate seawater can hold?

Iron increases the amount of phosphate that can stay dissolved before minerals crystallize and separate from the water. In the oxygen-poor, iron-rich conditions of early Earth, this allowed seawater to carry far more phosphate than once assumed.

Does this study prove that life began in seawater?

No, the researchers state that it does not prove life started in the ocean itself. Instead, it shows seawater could have supplied phosphate to many settings, including lakes, lagoons, and shorelines reached by sea spray.

Why is this research relevant to the search for life on Mars?

Ancient Mars had abundant water, widespread surface iron, and an atmosphere that was at times oxygen-poor. Simulations suggest iron-rich Martian water could have dissolved phosphate in a similar way, offering a possible pathway for life's chemistry beyond Earth.

Insights, Analysis, and Developments

Attribution/Source(s): This peer reviewed publication was selected for publishing by the editors of Disabled World (DW) due to its relevance to the disability community. Originally authored by University of Cambridge and published on 27 Sep 2022, this content may have been edited for style, clarity, or brevity.

* Editorial additions by Ian C. Langtree.