Here is a NASA JPL movie of a sunset on Mars in 2007, filmed by the Opportunity Rover:
According to JPL experts, Martian sunsets are blue because the dust in its thin atmosphere forward scatters – that is, brightens – blue wavelengths of light toward the observer much more efficiently than it does red wavelengths. This results in a bluish halo around the sun that’s there all the time but not very easily seen in the red sky until the sun gets down near the horizon, where the atmosphere is thicker and there’s a lot more dust.
All that dust also ensures a very long twilight glow after sunset, too.
Here’s another Opportunity sunset video from 2010:
By the way, Opportunity is celebrating its 10-year anniversary this year (that’s Earth years – a Martian year lasts 1.88 Earth years, or 668.59 sols, which is what they’ve decided to call a day on Mars apparently).
Fellow rover Spirit shut down in 2010, but Opportunity is still going strong. It’s exploring a different part of Mars than the Curiosity rover – the Eagle Crater region in MC-19 on this interactive map, where Curiosity is exploring Gale Crater in MC-23.
Right now Opportunity is climbing a hill and studying the geology there as it heads for its winter parking site.
Happy anniversary, Opportunity, and many more to come!