Ten years of full moons, in full color

Marcella Giulia Pace's collection of apparent colors documents the full moon from different locations across Italy. A red- or yellow-colored moon usually sits near the horizon, where its light takes a long path through Earth's atmosphere and loses some blue to scattering.

The Moon itself does not change color. It is gray-brown rock, sunlit, the same every month. What changes is the sky between us and it. Moonlight near the horizon travels a long, low path through Earth's atmosphere, and the air scatters blue light away far more than red — the same scattering that reddens sunsets. The low Moon looks red or yellow because the blue was taken out on the way. High overhead, the path is short, the scattering is small, and the Moon looks white. Ten years of full moons, photographed from different places across Italy, is a catalog of that filter: the same Moon, seen through different air, in different seasons, from different horizons.

There is a second layer in the collection. The Moon's surface is not uniform gray. The dark maria, the old lava plains, hold different minerals than the bright highlands, and those minerals tint the light by tiny amounts — slightly blue where titanium is rich, slightly warm where it is not. Processed views that boost those faint tints reveal the Moon in mineral color: a map of chemistry, written across the face. The apparent colors in this collection come from both sources at once: Earth's atmosphere doing the broad reddening, and the Moon's own surface doing the fine tinting.

That is the project's quiet insight. The Moon is the constant. Everything that varies — the red evenings, the yellow horizons, the pale high moons — is Earth: our air, our dust, our humidity, our horizon. A decade of full moons is a decade of weather, read off the face of a world that never changes.

Source: NASA APOD
Image credit: Marcella Giulia Pace, via NASA APOD