Earth may contain remnants of an ancient world. New study
New research proposes that enigmatic patches in Earth's mantle could be remnants of a hypothesized ancient planet that collided with our world around 4.5 billion years ago. Until now, experts believed that little of Theia, a Mars-sized object from which the Moon was formed, remained.
A team of scientists from China, the United States, and the United Kingdom has provided evidence in the journal, "Nature," supporting the existence of Theia's remnants not only on the Moon but also within the Earth.
Previously, proponents of the large impact theory believed that there was a massive collision around 4.5 billion years ago between the young Earth and a Mars-sized planet.
The ancient planet, known as Theia (or sometimes Orpheus), was completely destroyed. The majority of its mass and a part of the Earth's mantle were ejected into space, leading to the formation of the Moon. According to theory, only a tiny portion of Theia's remnants would have ended up embedded within our planet.
Based on this theory, the Earth and Moon should have different compositions. However, as Eureka Alert clarifies, "very precise isotope measurements have later revealed that the Earth and Moon's compositions are extremely similar, which challenges the conventional theory of Moon formation." But this lacked accurate analysis for confirmation.
The recent study, which largely relied on multiple computer simulations of the collision, provides more insight regarding the event and the corresponding theory. The researchers postulate that the massive collision of Theia and Earth could explain the existence of enormous 'Low Velocity Provinces' (LLVPs) in Earth's mantle, which have long puzzled geologists.
One of these LLVPs is located under the Pacific Ocean, while the other is beneath Africa. Where these occur, seismic waves move more slowly than in other parts of Earth's mantle, indicating they could have a different temperature and/or composition.
"Our findings challenge the traditional notion that the giant impact led to the homogenization of the early Earth," emphasized Prof. Deng Hongping from the Shanghai Astronomical Observatory (SHAO) of the Chinese Academy of Sciences. He added: "Instead, the Moon-forming giant impact appears to be the origin of the early mantle's heterogeneity and marks the starting point for the Earth's geological evolution over the course of 4.5 billion years."
The researchers estimate that around 2-3 percent of Earth's mass could be attributed to Theia, and the patches located under the tectonic plates could have evolved from a small amount of Theia's material that ended up in Earth's lower mantle.
Additionally, experts claim that the material in these patches is probably 2 to 3.5 percent denser and has higher iron content than the surrounding mantle, which might clarify the distinct spreading of seismic waves here.
Further evidence of Theia's significant impact on our planet is the stratification of Earth's mantle. The computer simulations revealed that after the collision, Theia and Earth's materials mixed in the upper mantle with a liquid magma ocean, whereas the lower mantle was relatively more solid and consisted mostly of Earth-like silicate materials. This stratification may still persist today.
Science Alert highlights that this research offers a novel toolkit for understanding our planet's history and origin, and even the Solar System's. Geophysicist Qian Yuan from Caltech, who also participated in this study, stated to the service that the ancient collision could be one of the fundamental factors making the Earth geologically distinct from other rocky planets.
This new understanding allows us to better comprehend other worlds and opens new perspectives for their potential future habitation.
