Bluish sunset as seen on Mars.
Photojournal: PIA19401
Source: NASA/JPL-Caltech/MSSS/Texas A&M Univ.
Published: May 1, 2019

NASA's Curiosity rover captured this sunset view at Mars' Gale crater in 2015.

Sunset Sequence

Sequence of Sun setting on the horizon of Mars.
The four images shown in sequence here were taken over a span of 6 minutes, 51 seconds.Credit: NASA/JPL-Caltech/MSSS/Texas A&M Univ.

This was the first sunset observed in color by Curiosity. The images come from the left-eye camera of the rover's Mast Camera (Mastcam). The color has been calibrated and white-balanced to remove camera artifacts. Mastcam sees color very similarly to what human eyes see, although it is actually a little less sensitive to blue than humans.

The rover's imaging team assembled a four-image sequence of the sunset over a span of 6 minutes and 51 seconds.

Dust in the Martian atmosphere has fine particles that permit blue light to penetrate the atmosphere more efficiently than longer-wavelength colors. That causes the blue colors in the mixed light coming from the Sun to stay closer to Sun's part of the sky, compared to the wider scattering of yellow and red colors.

The effect is most pronounced near sunset, when light from the Sun passes through a longer path in the atmosphere than it does at midday.


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