Europe shines brightly at night, as seen in this mosaic created from over 7000 pictures taken by astronauts on the International Space Station. This is the first nighttime mosaic of Europe in colour ever produced with calibrated space images.
The composition uses images from 2017 with a resolution of around 100 metres per pixel. Until 2021, the International Space Station was the only spacecraft suitable for capturing colour images of Earth at night. Resolution is equally important: astronauts were able to capture images at five metres per pixel, exceeding the capabilities that most satellites can currently offer.
Astronaut photography has emerged as the best source for scientists to map artificial light. All space agencies and their crews contribute to the effort, with ESA astronauts playing a vital role since Paolo Nespoli became one of the pioneers of nighttime photography from space in 2010.
“Most of the images that you see of Europe at night are artistic interpretations of black and white images, not real colour,” explains Alejandro Sánchez de Miguel from the Complutense University of Madrid and the Institute of Astrophysics of Andalusia in Spain.
By combining citizen science with artificial intelligence, the Cities at Night project created the mosaic by processing thousands of images and time-lapses, and correcting distortions in them. The missing patches at the bottom (north of Africa) and top (Scotland in the UK) of this mosaic are filled with data from NASA’s weather satellite Suomi NPP.
Different colours represent different lighting technologies, with warmer, redder tones generally indicating sodium light sources. The whiter and bluer emissions belong to light-emitting diode lamps, or LED technology, in our streets. The whitening of artificial light can be seen in this comparison between 2017 and 2022.
According to scientists, the transition towards white and blue-rich light radiation is eroding the natural nighttime cycles across the continent. Excessive lighting disrupts the circadian day-and-night rhythm of living organisms, including humans, with negative health effects on species and whole ecosystems.
A scientific study identified three major negative impacts: the suppression of melatonin, the response of insects and bats towards or away from light, and the visibility of stars in the night sky.
“Astronaut photography allows us to look back in time at global light pollution during periods when no colour-sensitive satellites existed,” adds Alejandro.
As part of the Plan-B project to protect our biodiversity and ecosystems, Cities at Night will release an app in 2026 that will allow Europeans to check how light pollution has evolved over time where they live.