The Same Sun, But Different Sunsets
If you enjoy watching the beautiful rose and peach sunsets on Earth, then you may be wondering if other planets in our solar system also have similar sunsets. Let’s explore different planets and their sunset colors. Geronimo Villanueva, a planetary scientist from NASA, created a sunset simulator that simulates the sunset on a few planets that are in our solar system. According to Villanueva, sunset colors broadly depend on the atmosphere of the planet, whether it is dominated by gases or dust, and the type of gases that the planet is surrounded by. Sunset colors on different planets are also influenced by the way particles on each planet scatter, reflect, or absorb sunlight. The shorter wavelength lights are blue, green, and violet and longer wavelength lights are red and yellow. So, depending on the atmosphere and the time of the day, each planet transfers either shorter wavelength light or longer wavelength light from the sun. This will create different hues in the sunsets on different planets.
For example, the Earth’s atmosphere has large contents of nitrogen and oxygen, which are more effective in scattering light. During the day, shorter wavelength lights (blue,green and violet) are scattered, which is why we see a blue sky. But during the sunset, the Sun’s rays have to travel farther, so longer wavelength lights (red and yellow) are scattered, making the sunset skies bright red or orange/peach hues.
If you take Uranus, which is largely made up of hydrogen, helium and methane, which absorb longer wavelength lights (red and yellow) and scatter shorter wavelength lights (blue and green), so the sunsets on Uranus display a bright blue sky that fades into royal blue with hints of turquoise.
On the other hand, if we look at the Martian sunset, which is mostly dominated by dust, and only contains 1/80th of atmospheric gas compared to earth, then the scattering of the light is affected by this dust. In his 2014 study on Mars, Professor Kurt Ehler found that dust particles scatter light in only one direction compared to the gas particles where light is scattered in all directions. He also explained that dust particles scatter lights with longer wavelengths (red and yellow) at much wider angles and that blue light is not scattered at wider angles, causing blue light to be concentrated almost 6 times as intense as the red light. Mars sunsets form a white halo-like disc around the sun, as the light doesn’t change its color when passing Mars's atmosphere, but you can see a bluish glow around the sun where the blue wavelength is concentrated. Further out, the sky is reddish as red wavelength is scattered at a wider angle.
Venus's atmosphere mainly consists of carbon dioxide with clouds of sulfuric acid and small traces of nitrogen. This atmospheric composition causes an extreme greenhouse effect, trapping the heat and surrounding it with dense clouds. The atmosphere on Venus is observed to be a good absorber of ultraviolet and blue light from the sun, and scatters the longer wavelength lights (red and yellow) casting bright golden-yellow skies during the sunset.
Picture Source: NASA (Sunset simulator and Earth and Mars sunsets)
