Astronomy Picture of the Day: Colors of the Moon

A spiral arrangement of differently colored full Moons showcases how our view of the lunar surface can vary with observing conditions. The images were collected by astrophotographer Marcella Giulia Pace over a decade at locations across Italy. Beyond Earth’s atmosphere, the Moon’s surface appears brownish gray, reflecting sunlight; the striking colors in the photographs arise largely from the atmosphere and the circumstances of observation rather than dramatic changes to the Moon itself.

Red or yellow hues are common when the Moon is near the horizon, because its light travels through more atmosphere, where blue wavelengths are scattered away; dust can intensify the effect. Blue Moons are rarer and may be associated with larger particles suspended in the atmosphere. The cause of the purple appearance remains uncertain and could involve several effects together. The final image shows the total lunar eclipse of July 2018: Earth’s shadow darkened the Moon, while sunlight refracted through Earth’s atmosphere gave it a faint red glow. The collection illustrates how atmospheric scattering, dust, and eclipses can make a familiar celestial object appear unexpectedly colorful.