Curiosity rover spies colorful iridescent clouds on Mars The Curiosity rover has witnessed a colorful marvel on Mars: Shining clouds. Color is rare in this frozen desert, apart from the predominant red. But in the skies above Curiosity, the clouds appear to almost sparkle with color. Unlike Earth, Mars doesn’t have many overcast, cloudy days. The red planet has a thin, dry atmosphere, so clouds tend to appear in the skies over the Martian equator when the planet is cold and farthest from the sun in its oval-shaped orbit every two Earth years . That changed two Earth years, or one Martian year, ago when Curiosity spotted clouds that arrived earlier and formed higher in the atmosphere than expected.