(CNN) – The Curiosity rover has seen a colorful wonder on the surface of Mars: bright clouds.
The color is rare in this frigid desert, with the exception of the dominant red. But in Curiosity’s sky, the clouds almost seem to glow with color.
Unlike Earth, Mars does not have many cloudy days. The red planet has a thin, dry atmosphere, so clouds tend to appear in the sky above the Martian equator when the planet is cold and farthest from the sun in its elliptical orbit every two years on Earth.
That changed two years ago on Earth, or one year on Mars, when Curiosity detected clouds that arrived earlier and formed higher than expected in the atmosphere.
In preparation for this event should it occur again, the Curiosity team on Earth sent the rover instructions to search for the first clouds in late January.
Curiosity’s camera captured the soft clouds filled with ice crystals. These ice crystals appear to glow because they scatter sunlight. In addition to being a fascinating sight, these images help scientists understand more about the formation of Martian clouds.
These early clouds form at a higher altitude and are cooler, so they are primarily made of dry ice (frozen carbon dioxide). Scientists are still studying them to find out why this happens.
Images taken by the rover’s navigation cameras in March, which capture black and white images, show ripples in the clouds. But the color photos taken by the camera on the rover mast after sunset reveal bright and glowing clouds.
Why do you see glowing colored clouds on Mars?
As the sun sets, these tall clouds become almost glowing, filled with ice crystals and reflecting faint sunlight. Then it darkens as the sunlight fades.
“If you see a cloud with a shimmering array of pastel colors, it’s because the particles in the cloud are nearly identical in size,” Mark Lemon, an atmospheric scientist at the Space Science Institute in Boulder, Colorado, said in a statement.
“This usually happens right after the clouds formed and they all grew at the same rate,” he added.
“I always marvel at the colors that come out: red, green, blue, and purple,” said Lemon. “It’s really cool to see something glowing with so much color on Mars.”
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