It is shown that for an ancient Moon (older than 4.5 billion years), the age cluster around 4.35 billion years naturally arises from the early thermal evolution of a magma ocean under the influence of tidal heating. Tidal heating in a partially molten magma ocean served as the primary internal heat source, compensating for rapid heat losses and maintaining a high-energy state for over 150 million years. As crystallization progressed, this stable phase ended with a sharp collapse of tidal heating, compressing the final solidification of the magma ocean into a short interval around 4.35 billion years. Thus, the tidal heat source separates the moment of the Moon's formation from the end of its magma ocean's solidification. The model also predicts asymmetric late-stage crystallization between the near and far sides, linking tidally modulated evolution to the long-term lunar dichotomy.
Lunar rocks brought a puzzle: their age is 4.35 billion years, but the Moon itself should have appeared 150 million years earlier. The missing time is hidden in tidal heating. When the Moon hung closer to Earth, Earth's gravity acted like tireless hands: it constantly kneaded and bent the satellite. From this, heat was generated inside — just like in a rapidly bending wire. The nature of these forces was unraveled by Isaac Newton. For a full 150 million years, the lunar ocean of magma would not solidify, kept warm by this cosmic workout. But as soon as the magma began to thicken, tidal heating weakened, and the last drops of liquid rock snapped into solid in an instant. That is the moment we mistakenly consider the Moon's birth. In reality, lunar rocks merely recorded the final exhalation of its internal heat. This also explains the difference between the near and far sides of the Moon: cooling happened unevenly. And today, the same hellish heating melts the interior of Io — Jupiter's moon, making it the most volcanic body in the system.
🎯 The two sides of the Moon are like two different worlds: the near side has smooth dark 'seas', while the far side is a chaos of mountains and craters. It turns out tidal heating is to blame: it made the magma solidify unevenly.