Why is Mars red and Earth blue

Curiosity: The sunset on Mars is blue

When Martians invite each other to take a romantic look at the sunset, the two of them do not look into the sunset, but into the evening blue. This is shown by photos recently taken by the Mars rover Curiosity.

Evening blue instead of evening red: Because of the dust in the atmosphere, the sky on Mars turns blue in the evening. (Photo: Nasa / JPL-Caltech / MSSS)
  1. Konstanz University of Applied Sciences, Constance
  2. DRÄXLMAIER Group, Vilsbiburg near Landshut

On April 15 of this year, Curiosity's 956th day on Mars (Sol 956), the robot succeeded for the first time in capturing a sunset in color with the mast camera.

Dust turns blue

The dust in the atmosphere is responsible for the blue color of the sunset, says Mark Lemmon of Texas A&M University in College Station, who planned the observations. The fine dust is the right size so that the blue components of the light can penetrate the atmosphere more efficiently than the longer-wave colors yellow and red.

"When the blue light is scattered by the dust, it stays more in the direction of the sun than the differently colored light"says Mark Lemmon. "The rest of the sky appears yellow to orange because the yellow and red light is scattered across the sky instead of being absorbed or staying close to the sun."

During the day, red dominates

According to the US space agency National Aeronautics And Space Administration (NASA), the effect is particularly effective at sunset, as the light from the lower-lying sun then takes a longer path through the atmosphere. During the day, however, the rust-red hues of the dust dominate.

The pictures of Sol 956 were taken after a sandstorm. Some of the dust was still hanging in the higher regions of the atmosphere. The scientists want to use the images to determine the vertical distribution of dust in the atmosphere. For this, the images have been slightly edited: the colors and the white balance have been adjusted a little.

The Mars rover Curiosity landed on Mars in early August 2012. Since then he has driven a good ten kilometers. Since September last year it has stood at the foot of Aeolis Mons or Mount Sharp in the middle of the Gale crater.