spaceSpace and Physics

Curiosity Snaps A Blue Sunset On Mars

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Caroline Reid

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Blue Sunset on Mars via NASA

#MarsSunset #Curiosity #WishYouWereHere

Earth's favorite Martian rover has sent back a stunning sunset photograph for its growing photo album. The image was taken by NASA's Curiosity rover on its 956th day exploring Mars.


It seems that Mars and Earth are complete opposites when it comes to the color of the sky: Earth has blue skies by day and warmer-colored sunsets, whereas Mars has rusty orange to yellow skies by day and dusky blue sunsets. It's the same sun that's illuminating both planets, so what's going on?

It turns out that the solution is down to the planets' different atmospheres.

When sunlight shines on Earth, the elements in the atmosphere scatter blue light in all directions, which is why we see a blue-colored sky. The atmosphere has very little effect on wavelengths at the red end of the spectrum, so these wavelengths of light plow straight through the atmosphere. This is why we see the sun as yellow.

During an Earth sunset, red light careens straight through the atmosphere to our eyes, and blue light is scattered away. When this happens, we can appreciate the warmer colors in the light spectrum.


Red skies over Rock Spire in 'Spirit of St. Louis Crater' on Mars taken by Curiosity via NASA

On Mars, instead of an oxygen- and nitrogen-rich atmosphere, there is a thin atmosphere filled with fine dust.

"The colors come from the fact that the very fine dust is the right size so that blue light penetrates the atmosphere slightly more efficiently," Curiosity team member Mark Lemmon said in a statement. "When the blue light scatters off the dust, it stays closer to the direction of the sun than light of other colors does. The rest of the sky is yellow to orange, as yellow and red light scatter all over the sky instead of being absorbed or staying close to the sun."

You can watch a timelapse of the sunset that was taken over a period of 6 minutes and 51 seconds.


Timelapse of blue sunset on Mars taken by Curiosity, via NASA

These photos have helped NASA to analyze the vertical distribution of dust in the Martian atmosphere. The photographs were taken during a lull in a sandstorm; however, there was still a lot of dust in the air.

For dreamers, these photos have got them wondering what colored sunsets other planets in the universe are experiencing.


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