About four billion years ago, microbes were the first signs of life on Earth. Scientists are still trying to determine when and how they appeared but it is clear that life’s emergence was intricately linked with the physical and chemical characteristics of the early Earth.
Dustin Trail, associate professor of the earth- and environmental sciences at Rochester University, says that it is reasonable to believe that life could have begun differently – or not at all – if the initial chemical characteristics of the planet’s surface were different.
What was Earth like billions of years ago? And what factors may have allowed life to develop? Trail and Thomas McCollom (a research associate at the University of Colorado Boulder), share key information in their quest to discover the truth. This research is important not only in discovering the origins but also for the search for life elsewhere on the planets.
Trail states that “We now live in an exciting time when humankind searches for life on other planets and in another planetary system.” Trail says that we don’t know the exact time or how life began on our planet. Our research helps to identify chemical pathways and conditions that may have supported the emergence of life. This work will be a major component in the search for life beyond our planet.
The role of metals in the development of life
The study of life and its origins usually involves many disciplines, including genomics, the study and analysis of genes and their functions, proteomics, the study and analysis of proteins, and metallomics which examines the role of metals in cellular functions. Trail and McCollom sought to discover what metals were available at the time microbes appeared billions of years ago.
Trail states that scientists assume all metals are available when hypotheses are presented for different origin-of-life scenarios because there haven’t been any studies that provide geologically solid constraints on the metal concentrations in fluids at the earliest time of Earth’s history.
Trail and McCollom investigated the composition and properties of fluids in Earth’s lithosphere, the outer layer that covers the crust and upper mantle billions of years ago to address this problem. These fluids in the lithospheric are crucial for transporting dissolved parts of minerals and rocks between Earth’s exterior and its interior.
Although researchers can’t directly measure the metals present billions of years ago in the Earth’s interior, scientists can determine the properties of fluids and infer which metals (and their concentrations) could have been transported to the exterior of Earth during the time that life first appeared on the planet.
Clues in billions-year-old minerals
Many times, the only source of direct information about Earth’s early history is from billion-year-old minerals and rocks. Because rocks and minerals contain information about Earth’s composition at the time of their formation, this is why it is so important.
They conducted high-pressure, high-temperature experiments on early-Earth zircons (a sturdy type of mineral that was collected in Western Australia) to determine oxygen pressure, chloramine content, and temperature for lithospheric fluids billions of years ago. These data were then used to build computer models. They were able to simulate the properties and then simulate which metals could have traveled through the fluids in order to reach the hydrothermal pool at Earth’s surface.
Understanding the origins of life
Researchers were shocked by the results of model simulations. Many origin-of-life researchers consider copper to be a probable component of the chemistry that could lead to life. Trail and McCollom didn’t find any evidence that copper would be abundant given the limitations of their analysis.
They did test for manganese, which may have been present at high levels. Although it is not often considered in origin-of-life scenarios, manganese today helps to form bones and aids enzymes in breaking down cholesterol and carbohydrates.
Trail states that “our research has shown that metals such as manganese could function as important links between Earth’s solid and emerging biological systems at its surface.”
Trail claims that the research will allow scientists who study the origin of life, to add more concrete data to their models and experiments.
“Experiments that are based on this information will lead to a better understanding of how life began.”
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