Sunsets on Mars Are Blue — the Exact Opposite of Earth's
Answers: “what color are sunsets on mars?”
Everyone knows an Earth sunset: the sky blushes orange and red as the Sun sinks. And everyone knows the daytime sky is blue. On Mars, both of these are flipped.
By day, the Martian sky is a hazy butterscotch or pinkish-tan color. And at sunset, the glow around the sinking Sun turns a cool, dusty blue. NASA’s rovers have photographed these blue Martian sunsets, and they look genuinely alien — the exact reverse of home.
The reason comes down to what’s floating in the air. On Earth, air molecules scatter blue light in all directions, painting the daytime sky blue, and at sunset the light travels through so much atmosphere that only red and orange survive — hence red sunsets.
Mars has a thin atmosphere, but it’s full of fine dust, and the size of those dust particles happens to be just right to scatter light the opposite way. The dust absorbs blue light across the daytime sky, leaving the tan color — but right around the Sun, where light passes most directly, blue light scatters forward toward your eyes, producing a glowing blue halo at sunset.
There’s a poignant footnote. In its final message before its 15-year mission ended in a global dust storm, NASA’s Opportunity rover’s last readable data was informally summarized by engineers as “my battery is low and it’s getting dark.” The little rover watched a lot of those strange blue sunsets before the dust finally won.
If humans ever stand on Mars, this is one of the first alien things they’ll notice: a rust-colored sky by day, and a cold blue sunset at night.