New research from Caltech offers compelling evidence that the early Earth was composed of hot, dry materials, suggesting water made a tardy entrance during Earth’s formative years. The study delves into magmas from different levels of Earth’s interior, yielding unique perspectives on our planet’s creation.
Caltech’s study proposes that the nascent Earth materialized from heated, arid substances, implying water only appeared late in Earth’s creation process. The investigation delivers clues from distinct mantle strata, suggesting substantial influx of volatile elements only occurred during the final stages of Earth’s formation, impacting prevailing theories on terrestrial planet formation.
The origins of our planets, moons, and asteroids date back to billions of years ago, taking shape in the vast disc of dust, gas, and rocky debris that encircled our fledgling sun. Today, scientists are still working tirelessly to comprehend the processes that culminated in the formation of these celestial bodies.
A method to investigate Earth’s formation involves analyzing magmas that emerge from deep within the planet’s core. The chemical imprints in these samples contain a historical account of the timing and type of materials that amalgamated to form Earth, in a similar vein to how fossils provide clues about Earth’s biological past.
The latest research from Caltech indicates that the infant Earth consolidated from hot and dry materials, suggesting water, the vital element for life’s evolution, made a belated appearance in the chronicle of Earth’s formation.
This collaborative study involved an international team of researchers working in the laboratories of Francois Tissot, assistant professor of geochemistry and Heritage Medical Research Institute Investigator; and Yigang Zhang of the University of Chinese Academy of Sciences. The research paper was recently published in the journal Science Advances, with Caltech graduate student Weiyi Liu listed as the principal author.
Though it remains impossible for humans to physically venture into our planet’s core, rocks from these depths can naturally surface as lavas. The source magmas of these lavas can derive from different depths within the Earth, such as the upper mantle or the lower mantle, extending to the core-mantle boundary.
Analogous to sampling different layers of a cake, researchers can study magmas from varying depths to comprehend the distinct “flavors” of Earth’s strata: the chemicals present and their proportions relative to each other.
Given that Earth’s formation was a gradual process, samples from the lower and upper mantle offer different insights into what transpired during Earth’s accretion. The recent study discovered that the early Earth was primarily made up of arid, rocky substances, with chemical signatures revealing a dearth of easily evaporated materials or “volatiles”, such as water and iodine.
Contrastingly, samples from the upper mantle showed a higher proportion of volatiles, threefold compared to the lower mantle. Based on these chemical proportions, Liu developed a model depicting Earth’s formation from hot, dry, rocky substances, with a significant addition of life-sustaining volatiles like water occurring in the final 15 percent or less of Earth’s formation.
This study is a pivotal addition to the theories of planet formation, a field characterized by vibrant scientific discourse and numerous paradigm shifts in recent decades. In this light, the study offers significant predictions for the nature of the constituents of other terrestrial planets like Mercury and Venus, which are presumed to have formed from similar dry materials.
“Outer space exploration is crucial because a water world is likely the best candidate for extraterrestrial life,” says Tissot. “However, the inner solar system warrants attention too. Venus hasn’t had a mission land on its surface for nearly four decades, and Mercury has never had one. Studying these worlds can enhance our understanding of how terrestrial planets like Earth came into being.”
Reference: “I/Pu reveals Earth mainly accreted from volatile-poor differentiated planetesimals” by Weiyi Liu, Yigang Zhang, François. L. H. Tissot, Guillaume Avice, Zhilin Ye and Qing-Zhu Yin, 5 July 2023, Science Advances.
The study’s co-authors include Zhang from the University of Chinese Academy of Sciences, Guillaume Avice from the Université Paris Cité, Institut de physique du globe de Paris, Zhilin Ye from the Chinese Academy of Sciences, and Qing-Zhu Yin from the University of California, Davis. The research was funded by the Chinese Academy of Sciences, the National Science Foundation, a Packard Fellowship for Science and Engineering, the Heritage Medical Research Institute, and Caltech.
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Frequently Asked Questions (FAQs) about Earth’s Formation
What are the main findings of the recent study from Caltech?
The study suggests that the early Earth was formed from hot, dry materials, indicating that water arrived late in the planet’s formation process. It provides new insights into the planet’s formation by studying magmas from different layers of the Earth’s mantle.
Who were the researchers involved in the study?
The research involved an international team of scientists working in the laboratories of Francois Tissot, assistant professor of geochemistry and Heritage Medical Research Institute Investigator, and Yigang Zhang of the University of Chinese Academy of Sciences. The first author of the research paper is Caltech graduate student Weiyi Liu.
Where was the study published?
The study was published in the journal Science Advances.
How does the study impact existing theories of terrestrial planet formation?
The study suggests that substantial additions of volatile elements, including water, only occurred during the final stages of Earth’s formation, which could impact prevailing theories of terrestrial planet formation. The study also makes important predictions for the nature of the building blocks of other terrestrial planets like Mercury and Venus.
What is the significance of the study’s findings on the search for extraterrestrial life?
The study underscores the importance of understanding the formation of terrestrial planets in the inner solar system, like Earth, in the search for extraterrestrial life. It suggests that missions to Venus and Mercury, planets expected to have formed from similarly dry materials, are needed to enhance our understanding of terrestrial planet formation.
More about Earth’s Formation
- Science Advances
- Caltech’s Earth Science Division
- University of Chinese Academy of Sciences
- Heritage Medical Research Institute
- National Science Foundation
- Packard Fellowship for Science and Engineering