Gazing down on planet Earth

It's Earth Day and we are high above the blue marble looking down on the border between the southern US states of Arkansas and Mississippi. Those small, blocky shapes are towns, fields and pastures and that teal green is the mighty Mississippi River. Anyone who has flown in the window seat of an aeroplane and gazed down at Earth below might wonder why the colours in this particular image are so unreal. That’s because they are. These images were taken in 2013 by Landsat 7, a Nasa satellite that uses thermal infrared sensors to help scientists better distinguish flora, fauna, water and man-made objects.
© Nasa