Blue Sunset on Mars
On April 15, 2015, the Curiosity rover witnessed this blue sunset over the crest of Gale Crater. Why does the Martian sunset appear blue?
It’s not a camera trick or an interplanetary Instagram filter. Due to their particular size, the gas molecules in Earth’s atmosphere scatter short wavelengths of light (blue and violet) away and allow long wavelengths to pass (red and orange). This scattering makes the midday sky appear blue away from the sun, and makes our sunsets appear red or orange as the light passes through more atmosphere on the way to our eyes.
The Martian atmosphere, on the other hand, contains dust particles of just the right diameter to scatter red and orange light and let blue light pass by, sort of the opposite of on Earth. Hence, a slightly sapphire sunset.
Read more and download hi-res images here!
(images via NASA/JPL)