For 40 years, NASA's Earth-observing Landsat satellites have been sending back stunning pictures of our planet's changing landscape from space.
The images below, showing the urbanization of Tucson, Arizona between 1965 and 2011, are a good example.
In the past four decades, Tucson has grown from about 260,000 people in 1970 to more than 520,000 people in 2011. There's also a lot less vegetation now, as shown by the lack of green in the more recent picture.
October 28, 2011 (Download the super large image)
August 22, 1965 (Download the super large image)
