Did You Know?
Sunsets on Mars are blue.
Earth and Mars are a bit like mirror worlds. Mars is the Red Planet. Earth is the pale blue dot. Mars is a frigid desert. Earth is full of water and life. But there's another curious difference. The sky on Mars is red, while its sunsets are blue.
The reason behind this is similar to why our sky is blue and our sunsets are red. The light from the Sun scatters based on what’s in the atmosphere. Sunlight comprises light of many different wavelengths, and molecules and dust particles only interact with specific waves. The scattering of light by these particles is key to the color that we see.
Mars’ atmosphere is very tenuous – its pressure is equivalent to about 1 percent of Earth’s. It is made of carbon dioxide and has a lot of dust. This fine dust tends to scatter red light so that the sky appears reddish, which lets the blue light through. On Earth, it is the other way around. Blue light bounces off air molecules giving our sky its characteristic hue.
At sunset light has a longer distance to travel within the atmosphere, so it scatters more. What is left is the color that we see. On Earth, we have a wider palette of reds, which is actually amplified by ash from volcanoes and dust from fires. On Mars, we get a cool blue hue.