Astronomy Picture of the Day

Explanation: The Moon is normally seen in subtle shades of grey or yellow. But small, measurable colour differences have been greatly exaggerated to make this telescopic, multicoloured, moonscape captured during the Moon's full phase. The different colours are recognized to correspond to real differences in the chemical makeup of the lunar surface. Blue hues reveal titanium rich areas while orange and purple colours show regions relatively poor in titanium and iron. The familiar Sea of Tranquility, or Mare Tranquillitatis, is the blue area in the upper right corner of the frame. White lines radiate across the orange-hued southern lunar highlands from 85 kilometre wide ray crater Tycho at bottom left. Above it, darker rays from crater Copernicus extend into the Sea of Rains (Mare Imbrium) at the upper left. Calibrated by rock samples from the Apollo missions, similar multicolour images from spacecraft have been used to explore the Moon's global surface composition.