Look a little closer
On Earth, a clear daytime sky is blue and sunset is red. Mars rover images can look reversed: suspended dust gives much of the sky a yellow-red cast, while blue light gathers close to the setting Sun.
Particles in the atmosphere sort the colors. In Earth's clean air, molecules much smaller than visible wavelengths scatter short blue light broadly. Mars instead has a thin atmosphere continually loaded with fine mineral dust.
The size and optical properties of Martian dust scatter light differently. Yellow and red wavelengths spread more widely across the sky, while blue light is scattered forward more efficiently and stays concentrated near the Sun's direction. This creates a narrow bluish halo.
Near the horizon, sunlight travels through a longer path of dust, making the contrast more noticeable. Rovers including Curiosity and Opportunity have photographed the effect around sunset.
This does not mean the entire Martian sunset resembles Earth's blue midday. Blue is mostly confined near the Sun while the surrounding sky remains tan and reddish. Dust amount, particle size and camera color processing can also change the appearance.
Opposite-looking sunsets on two planets arise from the same sunlight passing through different particles. A sky's color is not a fixed backdrop; it is produced by atmospheric composition and the path light takes through it.
