The research reveals clues to the physical and chemical properties of Earth when life is thought to have originated. – Zoo House News

The first signs of life appeared on Earth about four billion years ago in the form of microbes. While scientists are still pinpointing exactly when and how these microbes arose, it is clear that the origin of life is intimately intertwined with the chemical and physical properties of early Earth.

“It’s reasonable to assume that life might have started differently – or not at all – had the early chemistry of our planet been different,” says Dustin Trail, associate professor of earth and environmental sciences at the University of Rochester.

But what did Earth look like billions of years ago, and what properties might have contributed to the emergence of life? In an article published in Science, Trail and Thomas McCollom, a research associate at the University of Colorado Boulder, reveal key information to help find out. The research has important implications not only for discovering the origins of life, but also for the search for life on other planets.

“We are now in an exciting time as humanity searches for life on other planets and moons and in other planetary systems,” says Trail. “But we still don’t know how – or when really – life on our own planet began. Research like ours is helping to identify specific conditions and chemical pathways that may have aided the emergence of life, work that will surely play a prominent role in the search for life beyond our planet.”

The importance of metals for the origin of life

The study of life and its origins typically spans a variety of disciplines, including genomics, the study of genes and their functions; proteomics, the study of proteins; and an emerging field called metallomics, which studies the important role of metals in performing cellular functions. As life evolved, the need for certain metals changed, but Trail and McCollom wanted to determine what metals might have been available when microbes first appeared billions of years ago.

“In general, when proposing hypotheses for different formation scenarios, scientists have assumed that all metals were available because there were no studies that provided geologically robust constraints on metal concentrations in liquids for the earliest periods of Earth’s history,” says Trail.

Billions of years ago, to fill this gap, Trail and McCollom studied the composition and properties of fluids in the lithosphere — the Earth’s outer layer, which includes the crust and upper mantle. These lithospheric fluids are key pathways for transporting dissolved fragments of rocks and minerals between the Earth’s interior and hydrothermal pools on the outside, where microbial life may have thrived. While researchers can’t directly measure the metals that existed billions of years ago, by determining the properties of the fluids, they can deduce which metals — and the concentrations of the metals — might have been transported between the Earth’s interior and exterior during that time life arose on the planet.

Clues in minerals billions of years old

Rocks and minerals billions of years old are often the only direct sources of information about Earth’s earliest history. That’s because rocks and minerals contain information about the composition of the Earth at the time it was formed.

The researchers performed high-pressure and high-temperature experiments and applied these results to early Earth zircons, a robust mineral species collected from sites in Western Australia, to determine the oxygen pressure, chlorine content and temperature of lithospheric fluids billions of years ago. They then enter this information into computer models. The models allowed them to simulate the properties of the lithospheric fluids and, in turn, simulate which metals might have migrated through the fluids to reach hydrothermal pools at the Earth’s surface.

Understand how life came about

The researchers were surprised by what the model simulations showed. For example, many origin researchers believe copper is a likely component in the chemistry that might have given rise to life. But Trail and McCollom found no evidence that copper was abundant under the constraints in their analysis.

One metal they tested that may have been available in high concentrations was manganese. While it is rarely factored into origin of life scenarios, today manganese helps the body form bones and assists enzymes in breaking down carbohydrates and cholesterol.

“Our research shows that metals such as manganese can act as important links between the ‘solid’ earth and emerging biological systems at the surface,” says Trail.

According to Trail, the research will help scientists studying the origin of life to feed more concrete data into their experiments and models.

“Experiments designed with this information in mind will lead to a better understanding of the origin of life.”