Over 1.3 million photographs of Earth have been taken by astronauts aboard the International Space Station, with about 30 percent snapped at night. This huge catalog of images is available online through NASA's Gateway to Astronaut Photography of Earth, but only a small fraction of the photos have been cataloged or tagged with any helpful information about what part of the planet is displayed. Sounds like another task for the crowd.
The Complutense University of Madrid (UCM) has taken the lead here with a project dubbed Cities at Night that aims to catalog the images with the help of a little citizen science. On the site, a few apps let citizen scientists identify the cities that light up each image, and dig a little deeper and tag specific locations within each city that can be made out in the photos.
"Anyone can help," Alejandro Sanchez, a Ph.D. candidate at UCM, said in a release. "In fact, without the help of citizens, it is almost impossible to use these images scientifically. Algorithms cannot distinguish between stars, cities, and other objects, such as the moon. Humans are much more efficient for complex image analysis."
Many of the photos are remarkably clear, thanks to the European Space Agency's Nightpod system that was installed on the space station in 2012. Nightpod includes a motorized tripod that adjusts for the movement of the station, which is orbiting Earth at over 17,000 miles per hour.
So far, the cities in more than 20,000 photos have been identified by thousands of volunteers, but to ensure the highest degree of accuracy, Sanchez says it's best to have each photo re-confirmed by several different viewers.
For an easy introduction to the project, I've compiled a baker's dozen of photos from the collection that represent some of the most spectacular shots of Earth at night you're likely to see. Check out the gallery below.