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6d ago

Far-Side Moon Samples Link South Pole–Aitken Impact to Lunar Asymmetry

Isotopic measurements from Chang'e-6 samples indicate volatile loss from the South Pole–Aitken impact drove the Moon's hemispheric contrast.

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Our Moon Is Curiously Lopsided, And a Massive Impact Could Be to Blame
This artist’s concept shows the Moon’s hot interior and volcanism about 2 to 3 billion years ago. It is thought that volcanic activity on the lunar near side (the side facing Earth) helped create a landscape dominated by vast plains called mare, which are formed by molten rock that cooled and solidified. Credit: NASA/JPL-Caltech
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Overview

  • A PNAS study of four tiny basalt fragments from China's Chang'e-6 return finds enrichment in heavier potassium isotopes on the lunar far side compared with near-side basalts.
  • The team reports that potassium isotope shifts cannot be explained by normal magmatic processes, pointing to evaporation of lighter isotopes during the basin-forming impact.
  • Analyses compared far-side material with Apollo and Chang'e-5 near-side samples, while iron isotope differences appear consistent with magmatic effects.
  • Researchers argue that impact-driven volatile loss helps explain the near side's extensive mare volcanism versus the far side's thicker crust and ancient highlands.
  • Authors emphasize the conclusions are provisional given the small sample set and call for additional far-side samples to test how widespread the signature is, with potential implications for other rocky worlds shaped by giant collisions.