A team of researchers led by Katherine Bermingham from Rutgers University in New Brunswick has discovered that water did not arrive on Earth at such an early stage of its formation as previously assumed. This finding has fundamental implications for determining when and how life could have originated on our planet.

The study results, published in the scientific journal Geochimica et Cosmochimica Acta, support the hypothesis that water arrived during a late stage of Earth’s formation from dust and gas. In geological terms, this period is known as late accretion.

One of the goals of scientists studying the origin of life is to establish when the essential elements for its development appeared. For life to emerge, three fundamental ingredients are required: water, an energy source, and a set of organic compounds known as CHNOPS, which include carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur.

Professor Katherine Bermingham, from the Department of Earth and Planetary Sciences at Rutgers University, emphasized the significance of this finding: Determining when water arrived on our planet is one of the most important questions in planetary science. With this information, we can better pinpoint when and how life emerged on Earth.

Bermingham is a cosmogeochemist specializing in the chemical composition of materials in the solar system. Her research focuses on understanding the origin and evolution of rocky planets by analyzing terrestrial rocks and extraterrestrial materials such as meteorites.

For this study, the researchers used thermal ionization mass spectrometry along with a novel analytical method they developed. They examined molybdenum isotopes, a chemical element whose different variants provide key insights into planetary formation.

Earth Water Moon Life
A piece of iron meteorite Campo del Cielo, one of the samples measured in the study. Credit: Katherine Bermingham

According to Bermingham, the isotopic composition of molybdenum in terrestrial rocks provides a unique window into the events that occurred during the final stage of Earth’s core formation, a period that coincides with the formation of the Moon and during which the last 10% to 20% of Earth’s mass was assembled.

The scientists extracted molybdenum samples from meteorites stored at the National Museum of Natural History at the Smithsonian Institution. In the scientific community, meteorites are classified into two major groups: “CC-type,” which are believed to have formed in the outer region of the solar system, and “NC-type,” which exhibit characteristics indicating their origin in the inner and drier part of the solar system. This study focused on NC-type meteorites.

To determine the origin of Earth’s water, the team compared the isotopic composition of molybdenum in meteorites with that found in terrestrial rocks collected from Greenland, South Africa, Canada, the United States, and Japan. It is believed that the molybdenum present in these rocks comes from material added to Earth during the Moon-forming event, allowing researchers to trace when water might have arrived on our planet.

After analyzing the samples and comparing their isotopic signatures, the scientists concluded that terrestrial rocks are more similar to meteorites from the inner solar system (NC) than to those from the outer solar system (CC). This indicates that Earth did not receive a significant amount of water during the Moon-forming event, contrasting with previous theories suggesting that this event was key in delivering water to our planet.

Bermingham explained that the data obtained support the idea that water arrived in small quantities after the formation of the Moon, during a much later stage of Earth’s evolution. This interpretation suggests that late accretion played a more significant role in adding water to the planet than previously assumed.

The discovery that the Moon-forming event was not the primary mechanism for delivering water to Earth has profound implications for understanding the origin of life. If water arrived at a later stage, this means that the necessary conditions for life may have been established during a different period than previously thought.

In addition to Bermingham, the study’s co-authors include research assistant professor Linda Godfrey and researcher Hope Tornabene, both from the Department of Earth and Planetary Sciences at Rutgers University.

This finding represents a crucial step in understanding the processes that led to Earth’s formation as we know it and offers a new perspective on the emergence of one of the fundamental elements for life: water.

SOURCES

Rutgers, The State University of New Jersey

K.R. Bermingham, H.A. Tornabene, R.J. Walker, L.V. Godfrey, B.S. Meyer, P. Piccoli, S.J. Mojzsis. The non-carbonaceous nature of Earth’s late-stage accretion. Geochimica et Cosmochimica Acta, 2024; DOI: 10.1016/j.gca.2024.11.005

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