Nasa wants your help to solve a 300,000 piece puzzle.
No it's not your typical cardboard puzzle, but one containing hundreds of thousands of images taken by astronauts over more than 50 years - including several taken in orbit over New Zealand.
The American space agency is using crowd-sourcing to pinpoint locations of images taken at night from space from as far back as the 1960s, CNN reported.
The complete catalogue contains more than 1.8 million photos, about 1.3 million of them from the space station and roughly 30 per cent of them taken at night.
The night photos have coordinates of where they were taken, but not the direction they were shot or what they shot.
"We don't know which direction the astronaut pointed the camera, only where the station was at the time the image was taken," researcher Alejandro Sanchez said.
"Some images are bright cities, but others are small towns. It is like a puzzle with 300,000 pieces."
Nasa are asking people to help them identify what is on the ground and in the sky in those photographs.
First, the city will be identified and then individual suburbs and locations within that city.
The hope, Nasa says, is that the images "could help save energy, contribute to better human health and safety and improve our understanding of atmospheric chemistry. But scientists need your help to make that happen."
If you want to help go to, or just to have a look around, go to: http://www.citiesatnight.org/
The website has a photo of Christchurch they want help cataloging, and three photos taken while the space station was above New Zealand.
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