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At first glance, Earth and the Moon seem worlds apart—one teems with water and life, the other is a barren, airless rock. Yet, beneath their contrasting surfaces lies a surprising chemical kinship. The Moon’s regolith is rich in the same sand‑like materials that form Earth’s deserts, and many of the elements that compose our planet’s crust and mantle appear on the Moon in comparable proportions. Recent space missions have even revealed hidden reservoirs of ice beneath the lunar surface, adding another layer to this shared chemistry.
Oxygen, silicon, aluminum, iron, and calcium dominate the composition of Earth’s outer layers, and these elements are equally abundant in the Moon’s crust. Although the Moon lacks an atmosphere, it contains large quantities of oxygen bound in solid compounds. Conversely, heavy metals such as lead, mercury, and tin are comparatively scarce on the lunar surface.
Substances with low boiling points evaporate rapidly in the Moon’s extreme conditions—temperatures that can reach 127 °C (260 °F) and a near‑vacuum environment. Therefore, the discovery of ice in 1998 and again in 2009 was a major surprise. Frozen water has persisted for billions of years, buried beneath the surface and locked in permanent shadow near the poles. Scientists estimate that the Moon holds several hundred million tons of water, roughly equivalent to a medium‑sized lake.
On Earth, silicon dioxide manifests as sand, quartz, and natural glass. The Moon also contains vast amounts of this compound. Although the absence of wind and liquid water prevents natural weathering, countless meteorite impacts have pulverized lunar rocks into fine dust, creating a “regolith” that is rich in silicate particles. The intense heat of these impacts also generates green glass beads—tiny fragments of silicon dioxide fused together.
Aluminum is plentiful on both bodies, though it rarely exists as pure metal. On Earth, minerals such as corundum, ruby, and sapphire—formed from aluminum and oxygen—are prized for their hardness. Research from Washington University shows that most lunar aluminum is found in plagioclase feldspar, a mineral that can be ejected by powerful meteor strikes and occasionally reaches Earth as meteorites.
