Study reveals extraterrestrial masses spawned within Earth during Moon-forming impact
Theia's collision with Earth to form the moon may have also birthed enigmatic LLVPs, reveals a groundbreaking study This interdisciplinary research explores the possibility of these mysterious alien blobs originating from the same celestial event
Sign up for CNN's Wonder Theory science newsletter to delve into the mysteries of the universe. Stay updated with captivating news on groundbreaking discoveries, remarkable scientific advancements, and much more.
According to scientific consensus, billions of years ago, our planet experienced a significant collision with an ancient celestial body during its formation. This event resulted in the creation of the moon, which continues to adorn our night sky.
The giant-impact hypothesis, known as the theory, offers an explanation for numerous key characteristics of both the moon and Earth. However, a significant unanswered question persists at the heart of this hypothesis: What ultimately became of Theia? Concrete proof of its existence has yet to be discovered, as no remaining fragments of the celestial body have been located within the solar system. It has been widely presumed by scientists that any debris left behind by Theia on Earth would have been assimilated within the intense heat of our planet's core.
According to a recent study published in the journal Nature, remnants of the ancient planet Theia might still exist, preserved within Earth's mantle. These molten slabs of Theia could have become embedded in the mantle upon impact, eventually solidifying and creating a layer of the ancient planet's material resting approximately 1,800 miles (2,900 kilometers) beneath the Earth's surface, near the core.
A bold new idea
If the theory is correct, it would not only provide additional details to fill out the giant-impact hypothesis but also answer a lingering question for geophysicists.
They were already cognizant of the existence of two enormous, discrete entities deeply integrated within the Earth. These colossal enigmatic formations, known as large low-velocity provinces (LLVPs), were initially identified in the 1980s. One LLVP is situated beneath Africa, while the other resides beneath the Pacific Ocean.
Tourists explore the Mingsha Mountain and Crescent Spring scenic spot, with the Moon serving as a breathtaking backdrop, in Dunhuang, Jiuquan City, Gansu Province, China. (Photo by Zhang Xiaoliang/VCG via Getty Images)
Apollo 17 astronauts gathered rocks that unveil the actual age of the moon. These massive blobs, spanning thousands of kilometers, possess a higher density of iron compared to the encompassing mantle. Consequently, they stand out when measured through seismic waves. Nevertheless, scientists are still perplexed regarding the origins of these blobs, each of which surpasses the size of the moon.
Dr. Qian Yuan, a geophysicist and postdoctoral fellow at the California Institute of Technology, had a significant shift in his perception of LLVPs after attending a seminar in 2019 at Arizona State University, his alma mater. During the seminar, he gained new insights into Theia, the enigmatic projectile believed to have collided with Earth several billion years ago.
And, as a trained geophysicist, he knew of those mysterious blobs hidden in Earths mantle.
Yuan had a eureka moment, he said.
Immediately, he delved into scientific studies, scouring for any indication of prior suggestions that LLVPs could be remnants of Theia. Yet, no such proposals were found.
Initially, Yuan confided in his advisor solely regarding his theory.
"I was afraid of turning to other people because I (was) afraid others would think Im too crazy," Yuan said.
Interdisciplinary research
Yuan initially presented his idea in a paper submitted in 2021, which faced rejection on three occasions due to feedback from peer reviewers who highlighted the insufficiency of modeling pertaining to the giant impact.
Subsequently, Yuan serendipitously encountered scientists conducting research precisely aligned with the requirements of his study.
The researchers' study, which considered Theia's size and impact velocity in their modeling, indicates that the collision of the ancient planets probably didn't completely liquefy Earth's mantle. This allowed the remaining fragments of Theia to cool down and form solid structures, instead of merging with Earth's inner composition.
This rendering depicts the collision between Theia and the early Earth. Through the utilization of advanced simulations, mineral physics calculations, and seismic imaging, it has been determined that following this high-resolution giant impact, the lower portion of Earth's mantle predominantly remained in solid form. Additionally, sections of Theia's mantle, which contained a significant amount of iron, descended and gathered on Earth's core approximately 4.5 billion years ago. These remnants have endured throughout the history of Earth.
"According to Dr. Steve Desch, a professor of astrophysics at Arizona State's School of Earth and Space Exploration and a coauthor of the study, the Earth's mantle is not a solid rock, but rather a high-pressure magma with a gooey texture similar to peanut butter. It sits on a hot stove, creating a unique environment.
In this environment, the LLVPs, or the material that forms the jagged formations, cannot be too dense, as it would not be able to pile up. On the other hand, if it were too low in density, it would simply mix with the churning mantle."
The question posed was: What would be the density of the residue from Theia? Could it align with the density of the LLVPs?
(Desch had published his own paper in 2019 aiming to elucidate the density of the residue that Theia would have deposited.)
The researchers aimed to improve their modeling by increasing the resolution by 100 to 1,000 times compared to their previous attempts, Yuan explained. Surprisingly, the calculations confirmed their hypothesis. According to the models, if Theia had a particular size and composition, and collided with Earth at a specific velocity, it could have left behind substantial fragments within Earth's mantle and generated the debris that eventually formed our moon.
Yuan expressed his immense excitement, stating, "This groundbreaking modeling had never been accomplished before."
Building a Theory
The research study, released this week by Yuan et al., encompasses coauthors from diverse disciplines representing various institutions such as Arizona State University, Caltech, the Shanghai Astronomical Observatory, and NASA's Ames Research Center.
When questioned about the possibility of facing resistance or controversy regarding the ground-breaking notion that pieces of an ancient extraterrestrial planet lay concealed within the depths of the Earth, Yuan emphasized, "I want to emphasize that this is merely an idea, a hypothesis."
He further stated, "There is no definitive way to establish that this is undoubtedly the truth. I encourage others to engage in this research."
Desch expressed his belief that the work is persuasive and presents a compelling argument. He further commented that it appears to be somewhat obvious with the benefit of hindsight. While Dr. Seth Jacobson, an assistant professor of planetary science at Michigan State University, acknowledged the possibility that the theory may not gain widespread acceptance in the near future.
"These LLVPs are currently a topic of extensive research," commented Jacobson, who was not directly involved in the study. Moreover, the techniques employed to investigate them are continuously advancing.
While the hypothesis that Theia generated the LLVPs is undeniably intriguing and attention-grabbing, it is crucial to note that alternative hypotheses also exist."
Another theory suggests that LLVPs are piles of oceanic crust that have gradually submerged into the mantle over billions of years.
Jacobson added, "I highly doubt that proponents of alternative hypotheses regarding LLVP formation will discard their theories simply because this new hypothesis has emerged. I believe that the debate on this topic will persist for a significant period of time."
