Billions of years ago, in the giant disk of dust, gas, and rocky material that orbited our young sun, larger and larger bodies coalesced to eventually give rise to the planets, moons, and asteroids we see today. Scientists are still trying to understand the processes by which planets, including our home planet, were formed. One way researchers can study how Earth formed is to examine the magmas that flow up from deep within the planet’s interior. The chemical signatures from these samples contain a record of the timing and the nature of the materials that came together to form Earth — analogous to how fossils give us clues about Earth’s biological past.
Now, a study from Caltech shows that the early Earth accreted from hot and dry materials, indicating that our planet’s water — the crucial component for the evolution of life — must have arrived late in the history of Earth’s formation.
The study, involving an international team of researchers, was conducted 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. A paper describing the research appears in the journal Science Advances. Caltech graduate student Weiyi Liu is the paper’s first author.
Though humans do not have a way to journey into the interior of our planet, the rocks deep within the earth can naturally make their way to the surface in the form of lavas. The parental magmas of these lavas can originate from different depths within Earth, such as the upper mantle, which begins around 15 kilometers under the surface and extends for about 680 kilometers; or the lower mantle, which spans from a depth of 680 kilometers all the way to the core-mantle boundary at about 2,900 kilometers below our feet. Like sampling different layers of a cake — the frosting, the filling, the sponge — scientists can study magmas originating from different depths to understand the…