India, the beautiful view from above

NASA scientists have released new global maps of Earth at night, providing the clearest yet composite view of the patterns of human settlement across our planet.

Satellite images of Earth at night — often referred to as night lights — have been a source of curiosity for public and a tool for fundamental research. And now, NASA has released broad, beautiful pictures of night lights as observed in 2016, as well as a revised version of the 2012 map of different countries including India showing how humans have shaped the planet and lit up the darkness.

Produced every decade or so, such maps have spawned hundreds of pop-culture uses and dozens of economic, social science and environmental research projects.

In the years since the 2011 launch of the NASA-NOAA Suomi National Polar-orbiting Partnership (NPP) satellite, researchers have been analysing night lights data and developing new software and algorithms to make imagery clearer, more accurate and readily available. They are now on the verge of providing daily, high-definition views of Earth at night, and are targeting the release of such data to the science community later this year.

The principal challenge in night-time satellite imaging is accounting for the phases of the moon, which constantly varies the amount of light shining on Earth, though in predictable ways. Likewise, seasonal vegetation, clouds, aerosols, snow and ice cover, and even faint atmospheric emissions (such as airglow and auroras) change the way light is observed in different parts of the world.