A newly released satellite image of Egypt’s Nile river shows the river colored deep red, bringing to mind the biblical first plague in which the waters of the great river turned to blood.
But, this time at least, it is not the wrath of god that is responsible for the river’s crimson hue: The European Space Agency’s Sentinel-3A satellite, which took the picture, uses a radiometer to measure infrared energy.
The heat radiated by vegetation around the river is therefore responsible for the red color.
The satellite, launched in February, is designed to monitor environmental changes. It is the third of more than a dozen “eyes in the sky” that make up the Copernicus program, which the ESA describes as the most sophisticated Earth observation system ever launched.