Sometimes the most accurate image of an object isn’t the most informative. Images taken in grey-scale, true colour, or non-visual parts of the electromagnetic spectrum are sometimes rendered in false colour. We perceive the differences between colour more easily than we perceive, for example, the differences between shades of grey, so false-colour images often make details more visible to the human eye or convey information in a more effective way. The above image depicts our own moon’s northern hemisphere, and it was taken by the Galileo probe on a flyby in 1992—but it’s a false-colour mosaic, made up of 53 different images taken through three colour filters. These filters essentially reveal the moon’s surface composition. The red represents the lunar highlands, rich in iron; the purple represents pyroclastic deposits from explosive volcanic eruptions; and the blue through to orange represents volcanic lava flows—the bluer areas are richer in titanium. False-colour rendering allows this image to give us a fascinating insight into the moon’s composition, because the exaggerated colours help us immediately visualise the information. Interestingly, they even help us to visualise other celestial objects such as galaxies and nebulae, because most images featuring them are rendered in false-colour too.
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