More than three years after the National Aeronautics and Space Administration launched Curiosity to Mars, the rover has photographed its first sunset, reports the Washington Post.

What may come as a surprise to many people is that a sunset on the Red Planet is in the color blue. The reason has to do with dust particles.

"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 of Texas A&M University 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."

The Curiosity Rover's Twitter account tweeted a picture of the blue sunset on May 8, along with a quote from T.S. Eliot: "Let us go then, you and I. When the evening is spread out against the sky."

The blue sunset is in stark contrast to what the daytime sky looked like on Mars when Curiosity took the selfie below with a camera mounted on its robotic arm. 

Light from a setting sun passes through the planet's atmosphere on a longer path than at daytime, creating colors different than daytime, NASA explains. The Earth's sky looks different at sunset for the same reason, but our dust-free atmosphere causes different colors to appear.

The intense blue color seen through the rover's MastCam lens is "actually a little less sensitive to blue than people are," according to NASA. A human on Mars watching the sunset would see an even more vivid blue.

Curiosity took the sunset photographs from the Gale Crater on Mars in April. The images sent to Earth from the rover on April 15 were in black and white, but contain coded data from the MastCam revealing the blue color. NASA released the color image sequence on May 8.

The video below shows a Martian sunset, captured by NASA's Mars Exploration Rover Opportunity on Nov. 4 and 5, 2010, that appears bluish. The movie combines exposures taken through different camera filters and accelerates about 17 minutes of sunset into 30 seconds. The clip is the longest sunset movie from Mars in history.