As sand dust sweeps Beijing for the second time in a month, a "blue sun" appeared in the sky of China's capital city on March 28.

This scene would seem familiar to those who have seen pictures of the sun taken by rovers on Mars, where the sun always looks blue.

The "blue sun " is a phenomenon caused by a different light scattering pattern called Mie scattering. It occurs when there are fine particles like sand or water droplets. Dust particles scatter and absorb red light with a longer wavelength, reducing red light and giving the sun a bluish appearance.

Watch this video provided by Weather China, the online weather service of the China Meteorological Administration, to find out more about this sandstorm!

(All photos via CFP)

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