Sunsets on Mars look blue, while the daytime sky is a pinkish-red color.

The color of the sky depends on how light hits particles in the air. On Earth, tiny gas molecules scatter blue light in every direction, which makes our sky look blue during the day. At sunset on Earth, the light travels a long way and the blue light is scattered away, leaving only red.Mars has a very thin atmosphere filled with dust particles made of minerals like magnetite. These dust particles are about 0.5 to 1.0 micrometers wide. During the day, these particles absorb blue light and scatter red light, which gives the Martian sky its rusty or pink tint.When the sun sets on Mars, the sunlight must travel through much more dust to reach an observer. The dust scatters the red light away at wide angles. The blue light stays more concentrated and passes through the dust at narrow angles.This creates a blue glow or halo specifically around the sun. NASA landers like Viking 1 first photographed this blue sunset in 1976. Later rovers like Spirit, Opportunity, and Curiosity have confirmed this effect with many more photos. The blue light has a wavelength of about 450 to 495 nanometers, which is the part of the light spectrum that moves through Martian dust most easily at twilight.