The Moon has always been a plain, grayscale, landscape. Its plains and craters offer some variety, but the lunar surface blends into a uniform dullness. But when scientists reimagined it in false color, the familiar face turned alien—every hue a revelation about the rocks, lavas, and violent impacts that shaped our satellite’s past.
What exactly are we seeing?
This is the Moon, remixed. It’s a false color mosaic constructed from a series of 53 images taken through three spectral filters by Galileo’s imaging system as the spacecraft flew over the northern regions of the Moon. The images were taken on December 7, 1992. The part of the Moon visible from Earth is on the left side in this view.
Because some of those filters extended beyond the visible spectrum, the final colors you see are “false” — they don’t match what our eyes would see, but they carry real information.
The Pinkish and reddish tones mark the lunar highlands, areas of the crust relatively poor in titanium and iron. Blue to orange shades highlight basaltic lava plains (the maria), varying in titanium content and other minerals. Meanwhile, light blues and greens often trace newer, mineral-rich soils ejected by more recent impacts. In some cases, you’ll see blue “rays” emanating from fresh craters.
Take the dark blue patch just left of the oval basin called Crisium. That is Mare Tranquillitatis — yes, the same “Sea of Tranquility” where Apollo 11 first landed. The dark blue signals soil rich in titanium, far more so than the orange maria above it.
That contrast between bright colors is the whole point of this image. The colors accentuate subtle compositional differences that would otherwise be hidden in a standard grayscale or visible-light image.
The same image, using different color filters, can be seen below:
The story behind the shot
Galileo launched in 1989, bound for Jupiter. On its way, it conducted flybys of Earth, Venus, and the Moon. During one passage over the Moon on December 7, 1992, it snapped multiple images of the lunar surface through monochrome filters tuned to different wavelengths. Galileo’s primary mission was not lunar — it was to reach Jupiter in 1995 and study the giant planet and its moons. But along the way, it contributed to lunar science by giving us this rich map of a hemisphere we had seen only in shades until then.
To build a false-color mosaic like this, scientists have to collect dozens of images of the same region using filters that capture different wavelengths of light.
Some of these wavelengths are visible, some are invisible to the human eye. Each filter highlights subtle differences in surface composition, like variations in iron or titanium content. Later, they digitally stitch the images together into a seamless map and assign vivid colors to the wavelengths our eyes can’t normally see. The result looks psychedelic, but it’s not decoration: it’s a coded map where colors offer chemical clues. Scientists then cross-validate these maps with other methods (e.g. spectroscopy, seismic data, sample analysis).
Another remarkable false-color photograph was created in the same year with images snapped by NASA’s Galileo. This time, it’s a composite of 15 images of the Moon taken through three color filters. When this view was obtained, the spacecraft was 425,000 kilometers (262,000 miles) from the Moon and 69,000 kilometers (43,000 miles) from Earth. The coloring indicates the same things.
The original image also makes for a really cool poster. You can download it its full-resolution glory on this NASA page.
This article was originally published in March 2016 and has since been edited to include more information.
