Massive underground structure discovered beneath the Moon’s South Pole-Aitken basin

Key Points:

• Scientists have identified a massive, unusually dense underground structure beneath the Moon's South Pole-Aitken basin, the largest and oldest impact basin on the lunar far side, suggesting a violent early solar system history and a surprisingly stable lunar interior.
• The dense mass, weighing at least 2.18 × 10¹⁸ kilograms and extending to depths of at least 300 kilometers, may be either metal from the asteroid that formed the basin or dense oxide-rich material left over from the Moon's ancient magma ocean crystallization.
• This anomaly causes the basin floor to sag by 1 to 2 kilometers and is offset about 400 kilometers from the basin center, posing questions about the impact event and the distribution of lunar material.
• The survival of this dense mass for billions of years implies the Moon's deep mantle has been rigid and cool enough to prevent it from sinking, indicating that parts of the lunar interior lost much of their original heat early on and remained structurally preserved.
• The findings enhance the scientific importance of the South Pole-Aitken basin for future lunar missions, as studying this region could reveal crucial insights into the Moon's formation, cooling, and the early impact history of the solar system.