Earth's own pull may have given the Moon its two very different faces

Look up on a clear night and the Moon's face is marked with dark plains of old lava — but its far side, which never faces us, is bright, heavily cratered and covered in much thicker crust. That lopsided look has puzzled scientists since the first far-side photographs in 1959. Now a team led by Hejiu Hui at Nanjing University, in a study published in National Science Review, has studied the first rocks ever brought back from the far side — about 1,935 grams (about 4.3 pounds) of soil and rock returned by China's Chang'e-6 mission in June 2024 — and compared them with near-side samples from Apollo and Chang'e-5. The deep interior looks much the same on both sides, but the far-side crust is richer in magnesium and strikingly short of KREEP, a mix of elements linked to volcanic heat. Their explanation: once the young Moon settled into always showing Earth the same face, Earth's tidal pull warmed the near side more, sending hot magma flowing toward the far side to build its thicker crust while the heat-making leftovers pooled underneath the face we see — later feeding its dark lava plains. The team is careful to call this a plausible explanation, not a proven one: every far-side sample so far comes from a single landing site, and rocks from other far-side regions will be needed to settle it.