Water on Earth appeared during the last 15% of the formation of the planet

According to a new study, chemical signs indicated that the Earth was formed from dry rocky materials. However, the living water and other necessary volatile substances appeared much later than it was assumed by past theoretical models. The results of the study are published in the journal Science Advanced.

New research showed that the Earth was first formed from hot, dry and rocky materials, and later water appeared. Photo: Unsplash

This research is important for our understanding of the formation of the planet, which continues to cause lively scientific discussions. In addition, it provides valuable information about the structure of other planets, such as Mercury and Venus, which are also believed to have formed from similar dry materials.

Earth and water in its interior

Although people physically cannot descend into the depths of our planet, rocks from its depths can come to the surface naturally in the form of volcanic lava. These lavas are formed from “mother magma”, which can come from different depths of the Earth. For example, the upper mantle begins about 15 km below the surface and extends about 680 km downwards. The lower mantle begins at a depth of 680 km. It extends to the core-mantle boundary, about 2,900 km below our feet. Scientists can chemically compare these two different types of magma to understand the distinct characteristics of the Earth’s layers.

Since the formation of the Earth occurred gradually through the accumulation of materials, samples obtained from the lower and upper mantle gave clear clues about the processes that unfolded during the accretion of the Earth.

Last 15%

In a new study, scientists found that in the early stages our planet consisted mainly of dry and rocky materials. Studying chemical signs deep in the interior of the Earth, they noticed a clear absence of rapidly evaporating volatile substances such as water and iodine. In contrast, when analyzing samples from the upper mantle, they found a significantly higher concentration of volatile substances. The proportions of these substances were three times greater than in the lower mantle.

Based on these chemical ratios, a graduate student at the California Institute of Technology and the lead author of the study, Weiyi Liu, developed a model that provided valuable information. 

The model showed that the Earth was first formed from hot, dry and rocky materials. She also suggested that the addition of the main volatile substances necessary for life, including water, occurred relatively late in the formation of the Earth — during the last 15% of the planet’s development or even less.

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