In a potentially groundbreaking discovery, scientists from the China Academy of Sciences have presented new evidence supporting the theory that a significant portion of Theia, a Mars-sized protoplanet, may have become deeply embedded within Earth during a cataclysmic collision 4.5 billion years ago. This collision is believed to have led to the formation of the Moon, but not all researchers have agreed with this hypothesis until now.
The research team examined large low-velocity provinces (LLVPs), massive masses of material buried beneath the African continent and the Pacific Ocean. Their findings, detailed in a recent paper published in Nature, involved intricate fluid dynamics simulations to understand the possible origin of these enigmatic blobs.
By simulating the impact of a Theia-like object colliding with Earth, the researchers concluded that the upper part of Earth’s mantle would have been melted during the event, allowing around ten percent of the object to sink deep into Earth, near its core. Over time, these embedded remnants of Theia would have been influenced by convection currents, evolving into the two LLVPs.
Previous simulations had suggested that only trace amounts of Theia became integrated into Earth. However, the new study proposes that a more substantial portion of the Mars-sized protoplanet, approximately ten percent, may have been trapped within our planet, accounting for roughly two to three percent of Earth’s total mass.
This revelation also provides a potential means of testing the theory. “In most of the Moon-forming impact simulations, most of the lunar materials come from the impactor, so we expect future missions can get lunar mantle rocks and compare that with the mantle blobs to see if they share the same chemical signatures,” explained lead author Qian Yuan, a geophysicist at Caltech. “If the lunar mantle rock and LLVP-related basalts share the same chemical signatures, they should originate from Theia.”
While these findings are captivating, numerous questions remain, and not all experts fully agree with the conclusions regarding the LLVPs’ origins. Dr. Robin Canup, a planetary scientist at the Southwest Research Institute in Boulder, Colorado, not involved in the study, praised the findings as “exciting and provocative.” However, he also noted the mystery of how the purported Theia fragments managed to avoid becoming mixed into Earth’s mantle over 4.5 billion years.
Geodynamicist Maxim Ballmer of University College London, also not involved in the study, pointed out that competing theories suggest that the lower layer of Earth’s mantle might have formed different-density blobs independently.
Peering back into Earth’s prehistory remains a formidable challenge, as drilling to the planet’s core is beyond our technological capabilities. Whether the Moon’s surface will provide supporting evidence for Yuan and his colleagues’ theory remains uncertain. Nonetheless, the ongoing exploration of these mysteries promises to be a captivating and evolving scientific endeavor.
