Mars is often called the Red Planet, but a recent image captured by NASA’s Perseverance rover from the surface would go some way to contradicting that.
Earlier this year, Perseverance snapped a sunset from Mars in which the Sun looks blue, a sight which would never be seen from our own planet.
The photograph was taken on the rover’s 842nd day on the planet, and shows a Martian horizon with the sun setting behind causing an eerily cool glow.
Because of Mars’ distance from the Sun, it gets less sunlight than we do on Earth. Even at its sunniest, it gets less than half our quota of light from the star.
And the planet’s atmosphere, which is weaker than Earth’s, is mainly made up of carbon dioxide, with a small amount of nitrogen and a trace of oxygen.
This gaseous mix and weak atmosphere causes the light to scatter in a blue haze across the sky.
It’s the same process which gives us our blue sky during the daytime, when the light has less atmosphere to penetrate before it reaches our eyes.
On Earth, this changes when the sun dips below the horizon, and the light has more atmosphere to penetrate, filtering our blue and violet wavelengths, leaving only reds and oranges.
Meanwhile on Mars, the sunlight interacts with the dust hanging in the atmosphere, scattering red light during the day. At twilight, that red light is filtered away, leaving blues.
Atmospheric scientist Mark Lemmon of Texas A&M University told Science Alert: "The colours come from the fact that the very fine dust is the right size so that blue light penetrates the atmosphere slightly more efficiently.
“When the blue light scatters off the dust, it stays closer to the direction of the Sun than light of other colours 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.”
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