By Sophie Lin – Technology Editor
Lunar Samples Solve the Mystery of the Moon’s Two Hemispheres
This collection of rocks gives scientists a direct look at geological materials previously hidden from Earth.
Earth’s nearest celestial neighbor splits cleanly into two distinct hemispheres. The near side features wide volcanic plains rich in potassium, rare earth elements, and phosphorus. In contrast, Science Daily reported that the far side hosts an ancient cover of mountainous highlands packed with craters and a significantly thicker crust.
Basalt and Anorthosite Analyses Challenge Internal Composition Theories
Previous hypotheses assumed a deep internal compositional difference between the two halves. Chemical analyses of basalt and anorthosite rock samples challenge that idea. They show the moon’s internal mantle shares a uniform chemical makeup across both hemispheres, pointing to a thermal origin for the asymmetry rather than a fundamentally divided interior.
Crustal rocks retrieved from the far side contain higher magnesium proportions paired with significantly lower concentrations of rare earth elements compared to samples from Apollo missions. These mineral gaps show that crust formation processes varied between the two zones despite identical mantle ingredients.
Tidal Locking and Early Gravitational Forces Heat the Lunar Interior
The research team developed a scientific model explaining this split through tidal locking. As early gravitational forces bound the moon’s rotation to Earth while the two bodies sat in close proximity, Earth’s gravity heated the moon’s interior unevenly. This thermal gradient triggered convection currents within the lunar magma ocean.
Magnesium-Laden Magma Flows Form the Thick Far-Side Crust
Hotter magma laden with magnesium compounds flowed toward the far side, cooling to form that hemisphere’s thick crust. Meanwhile, residual molten materials and active volcanic elements concentrated on the near side. That uneven thermal distribution left behind the starkly divided lunar geography visible today.
Analysis of basalt samples confirms that internal heating dynamics drove the crustal thickening on the hemisphere facing away from Earth, resolving the debate over lunar dichotomy without requiring exotic mantle compositions.
