Mascons

Mascons (mass concentrations) are mysterious dense regions beneath the Moon's surface that cause gravitational anomalies first detected by NASA's Lunar Orbiter missions. These hidden, high-density masses—likely ancient asteroid metals or solidified lava—distort spacecraft orbits and create local gravity fields 50% stronger than surrounding areas. Found primarily under large impact basins like Mare Imbrium, they may explain why the Moon always shows its near side to Earth. Their discovery revolutionized planetary science, proving celestial bodies aren't uniformly dense. Some theories suggest mascons could be remnants of the colossal impact that formed the Moon, preserved for billions of years beneath the lunar crust.