The prevailing theory of how the Moon formed suggests that around 4.5 billion years ago, a massive object called Theia collided with Earth, resulting in the ejection of debris that eventually coalesced and formed our Moon. However, recent research conducted by scientists from China, the US, and the UK has revealed compelling evidence that not only did some fragments of Theia end up in the Moon, but they also made their way inside our planet. This groundbreaking discovery has the potential to solve a longstanding mystery puzzling scientists for over a decade – the existence of dense, continent-sized blobs buried deep within Earth’s mantle.
Deep within the core-mantle boundary, approximately 2,900 kilometers (1,800 miles) beneath the Earth’s surface, lies a geological phenomenon known as large low-shear-velocity provinces (LLVPs). These large, dense regions have been the subject of intense scientific scrutiny, with multiple theories proposed for their formation. Previously, it was believed that LLVPs were generated by internal processes within Earth, such as remnants of old tectonic slabs or a magma ocean. However, the recent study challenges this notion and introduces a new hypothesis – these LLVPs may have originated from Theia.
To investigate the possibility of Theia’s contribution to Earth’s geological composition, the research team conducted a series of computer simulations. These simulations aimed to explore the post-impact effects of Theia on the structure and composition of Earth. The results revealed two significant findings that support the hypothesis of Theia’s presence in Earth’s mantle.
The computer simulations showed that during the impact event, Earth and Theia materials mixed in the upper mantle, forming a liquid magma ocean. In contrast, the lower mantle remained relatively solid, consisting mainly of silicate Earth material. This stratification, which aligns with seismic data, may still persist today, providing a potential trace of Theia’s influence on Earth’s mantle.
Another important discovery from the simulations is the potential role of Theia in the formation of LLVPs. Small fragments of Theia, measuring only tens of kilometers across, could have sunk to the core-mantle boundary. Over time, these fragments would accumulate, gradually growing into the large low-shear-velocity provinces observed today. The researchers estimated that around 2 to 3 percent of Earth’s mass could be attributed to Theia, and the LLVP material is expected to be denser and richer in iron compared to the surrounding mantle.
The implications of Theia’s contribution to Earth’s geological evolution are far-reaching. By comparing lunar mantle rocks obtained from future missions with the mantle blobs of Earth, scientists may uncover shared chemical signatures that validate the hypothesis. This would provide invaluable insights into the history and formation of our planet and the Solar System as a whole. Furthermore, these findings can enhance our understanding of other celestial bodies and their potential habitability, broadening our perspective on the search for exoplanets similar to Earth.
One of the remarkable aspects of Earth is its distinctiveness in the Milky Way. Despite the countless exoplanets discovered, none has been identified as an exact replica of our home planet. The giant impact theory presents a compelling explanation for why Earth stands alone in its characteristics. The collision with Theia and subsequent mixing of materials could account for the specific composition and geological features that distinguish Earth from other celestial bodies.
The discovery of Theia’s remnants within Earth opens up a fresh avenue of understanding in the study of our planet’s history and formation. The role of Theia in the creation of the Moon and the subsequent impact on Earth’s mantle sheds light on the complexities and intricacies of geological evolution. As scientists continue to explore this fascinating area of research, we may unlock vital insights into our place in the universe and the possibilities of life beyond our world.