A recent study published in Science Advances has unveiled that the moon’s interior is not uniform, with the side facing Earth exhibiting significantly higher temperatures compared to the far side. This groundbreaking discovery is rooted in a meticulous analysis of data gathered by NASA’s GRAIL mission (Gravity Recovery and Interior Laboratory), which mapped the moon’s gravitational field with unparalleled precision.
The GRAIL mission, operational from 2011 to 2012, involved the deployment of two spacecraft orbiting the moon to measure minute variations in its gravitational pull. By observing how Earth’s gravity influenced the motion of these spacecraft, scientists were able to forge a high-resolution map of the moon’s gravitational field. Ryan Park and his research team at NASA’s Jet Propulsion Laboratory meticulously analyzed this data to explore how the moon’s shape alters under the influence of Earth’s tidal forces.
The analysis revealed that the moon’s near side—constantly facing Earth—is approximately 72 percent more deformable than what would be expected if its interior were entirely symmetrical. This enhanced deformability indicates a warmer interior beneath the near side, making it softer and more prone to tidal stretching. “Our study shows that the moon’s interior is not uniform: the side facing Earth – the nearside – is warmer and more geologically active deep down than the farside,” stated Park, the lead author of the study.
This pronounced internal temperature discrepancy aligns with existing knowledge regarding the moon’s volcanic activity and the concentration of radioactive elements, such as uranium and thorium, which are notably present near the lunar surface on the near side. Sean Solomon from Columbia University emphasized that this asymmetry corroborates theories surrounding the moon’s volcanic history and the internal heating attributed to radioactive decay.
The temperature imbalance raises intriguing questions regarding the formation of the moon’s lopsided interior. One hypothesis posits that substantial impacts over billions of years may have induced structural and thermal disruptions, further contributing to this asymmetry. The findings shed vital light on the cooling and solidification processes of the celestial body post-formation, illustrating a dynamic and evolving satellite rather than a static and uniform entity.
To further unravel the mysteries of the moon’s internal structure, NASA is set to deploy seismic instruments on the lunar far side. The forthcoming Farside Seismic Suite mission, anticipated to launch in 2026, aims to measure moonquakes and gather direct data regarding the moon’s internal temperature and composition. These seismic measurements will complement the gravitational data obtained from the GRAIL mission, enabling scientists to gain deeper insights into the causes and extent of the moon’s internal temperature variations.
This research is poised to enrich our understanding of lunar geology and the processes that shape not only the moon but also other rocky bodies within our solar system.
