A cross-sectional view showing how ilmenite, a high-density mineral containing titanium and iron, has penetrated into the lunar mantle. Provided by Adrien Broquet/University of Arizona & Audrey Lasbordes
Research results have revealed that heavy metal on the moon’s surface sank inside the moon in its early days and then erupted again as lava.
The research team led by Professor Jeff Andrews-Hanna of the University of Arizona’s Lunar and Planetary Laboratory (LPL) used data on changes in the lunar gravitational field to determine that heavy rare metals such as titanium sank into the mantle in the early stages of the moon’s formation and were later erupted on the surface due to volcanic activity. The research results were published in the international academic journal ‘Nature Geoscience’ on the 8th (local time).
It is known that the moon was created from the agglomeration of rocks that formed when a small planet collided with the Earth about 4.5 billion years ago. The explanation for the moon’s origin was constructed by combining theoretical models with rock samples collected during the Apollo mission more than 50 years ago.
High concentrations of titanium were detected in basalt samples that solidified lava on the lunar surface. Later, satellite observations revealed that basalt was rich in titanium. It has not yet been revealed exactly how titanium reached the lunar surface.
The research team explained, “According to the moon formation model, the moon was covered with a sea of hot magma, then slowly cooled and solidified,” and added, “Ilmenite, a high-density mineral containing titanium and iron, crystallized from the last remaining residue in the magma sea.” did.
The analysis is that ilmenite is denser than the mantle, causing gravitational instability, sinking into the lunar interior in steps, mixing with the mantle, melting, and then erupting as titanium-rich lava and returning to the lunar surface.
To find evidence to explain this process, the research team looked for gravitational anomalies and ilmenite detected by NASA’s Lunar Exploration Mission (GRAIL), which measured minute changes in gravity while orbiting the moon between 2011 and 2012. Simulations of ore layers sinking in the lunar mantle were compared.
As a result, it was confirmed that the simulation of ilmenite sinking in steps and the ‘pattern’ left in the gravitational field changes measured by the GRAIL mission matched. Furthermore, the research team also confirmed that the ilmenite mineral layer sank about 4.22 billion years ago.
Professor Andrews-Hanna said, “We have obtained physical evidence of what happened inside the Moon during a critical stage of its evolution. The Moon’s early history was recorded beneath its surface, and the right combination of models and data is needed to uncover this story. “It is necessary,” he said.
