Mars is famous for its rusty-red landscape, dusty plains and barren rocky terrain.
But every so often, the Red Planet produces something that looks almost completely out of place.
A shimmering sky.
NASA’s Curiosity rover has captured remarkably colorful clouds floating high above the Martian surface, with subtle shades of red, green, blue and purple appearing across the formations.
The clouds are known as iridescent, or “mother-of-pearl,” clouds, and they are among the most visually unusual atmospheric phenomena ever photographed on Mars.
Although the images may look almost like an artistic creation, the phenomenon is real.
And the science behind it is just as fascinating as the photographs themselves.
A Strange Glow in the Martian Twilight
Curiosity has been exploring Mars since landing inside Gale Crater in August 2012.
Over the years, the rover has photographed enormous landscapes, ancient rocks, dust storms and sunsets.
But the Martian atmosphere can also produce much subtler sights.
Among them are clouds that become visible around sunset, when the Sun is low enough on the horizon to illuminate high-altitude clouds while the surface below is already falling into darkness.
NASA calls these noctilucent, or “night-shining,” clouds.
In February 2025, NASA released new observations made by Curiosity showing clouds drifting through the Martian sky during twilight. The rover's Mastcam camera recorded the scene over approximately 16 minutes on Jan. 17, 2025.
The resulting imagery showed red- and green-tinged clouds moving across the sky.
And under the right conditions, some of these clouds can display an even more extraordinary effect: iridescence.
Instead of appearing as ordinary white or gray clouds, they can shimmer with pastel colors.
What Are “Mother-of-Pearl” Clouds?
The phrase “mother-of-pearl” refers to the soft, shimmering colors sometimes seen on the surface of pearls.
In atmospheric science, iridescence occurs when sunlight interacts with very small particles within a cloud.
The particles scatter light in ways that can produce different colors depending on their size and arrangement.
NASA atmospheric scientist Mark Lemmon has explained that when cloud particles are nearly identical in size, they can produce particularly noticeable pastel colors.
That is what makes these Martian clouds so interesting.
The colors are not painted onto the clouds.
They are created by light.
NASA has described the phenomenon as one of the more colorful sights found on the Red Planet, with observations showing shades including reds, greens, blues and purples.
From a distance, the effect can look almost artificial.
But it is actually a natural consequence of sunlight interacting with microscopic ice particles high in the Martian atmosphere.
Not Every Martian Cloud Is Made of Dry Ice
One of the most fascinating aspects of these clouds is what they may be made of.
Mars has a very thin atmosphere, and more than 95% of it is carbon dioxide.
Under extremely cold conditions high above the surface, carbon dioxide can freeze into solid carbon dioxide — commonly known as dry ice.
NASA's observations indicate that some of the high-altitude clouds seen by Curiosity are made of carbon dioxide ice.
But there is an important distinction.
Not all Martian clouds are made of frozen carbon dioxide.
Many of the clouds found closer to the surface are made of water ice, much like clouds on Earth.
NASA explains that Martian clouds can consist of either water ice or, at higher altitudes and lower temperatures, carbon dioxide ice.
The especially high clouds associated with the iridescent phenomenon appear to be made of carbon dioxide ice because temperatures at those elevations are cold enough for CO₂ to freeze.
That makes them very different from most familiar clouds here on Earth.
Clouds Do Not Usually Form This High
The altitude of these clouds is another reason scientists find them so interesting.
NASA estimates that the carbon-dioxide-ice clouds in the 2025 Curiosity observations were approximately 37 to 50 miles (60 to 80 kilometers) above the Martian surface.
That is extraordinarily high.
For comparison, most clouds in Earth's troposphere occur much closer to the surface.