NASA's Curiosity rover captured images of clouds on the surface of Mars, as described in its blog post: "Light clouds laden with ice crystals that scattered sunset light, some shimmering with color."
The shimmering appearance of icy white clouds in the Martian atmosphere surprised NASA scientists, appearing in their delicate formations in exquisite shapes.
According to NASA, clouds are a rare climatic phenomenon on Mars compared to Earth, thanks to the red planet's thin and dry atmosphere, but they are certainly well known.
However, a number of unusual cloud formations recently observed by the agency's Curiosity rover have been somewhat remarkable, forming earlier than expected in a Martian year and at higher altitudes in the atmosphere.
Two years ago, clouds began to appear in the Martian sky earlier than was generally expected (NASA)
According to the US space agency, clouds on Mars usually form around the equator on the coldest day of the year on a planet, when Mars is farthest from the sun in its semi-elliptical orbit.
But two years ago, clouds began to appear earlier than was generally expected, and this year it was repeated as well, as clouds appeared earlier in January, and at a higher altitude as well.
NASA researchers are not entirely sure, but these unusual properties may be caused by the fact that these clouds are not clouds of water ice. The majority of Martian clouds are made of water ice crystals that shimmer with light reflected from the sun, and these clouds usually form at a maximum altitude of 60 km.
So more analysis is needed to be sure, but the high clouds that Curiosity observed recently may be of a different type, they may be made of frozen carbon dioxide (also known as dry ice) suspended in a higher and colder part of the sky, but no matter what they are. It is well worth seeing thanks to Curiosity's strong vision.
Black and white images show clouds' wavy details more clearly (NASA)
Curiosity provided both black and white and color photos, which show the wavy details of the clouds more clearly, while the color images from the rover's mast camera are stitched together from several truly stunning images.
In its description, NASA stated that it was "observed just after sunset, as its ice crystals capture the faint light, making them appear to glow against the dark sky."
These twilight clouds, also known as nocturnal (nightly shining) clouds, get brighter when filled with crystals, and then darken after the sun's position in the sky drops below its height, which is just one useful clue that scientists use to determine its height.
Mars' iridescent clouds (also known as "mother of pearl") are an even more attractive phenomenon, as they reveal a subtle palette of different colors in the clouds, which tells us how they formed.
Twilight clouds, also known as nocturnal clouds, get brighter when filled with crystals (NASA)
"If you see a cloud with a bright, shimmering color range, it's because all the cloud particles are nearly identical in size," explains atmospheric scientist Mark Lemmon of the Space Science Institute in Boulder, Colorado, USA. "This usually happens." Immediately after the formation of clouds and the growth of all its particles at the same rate."
While the colors are faint, they're still some of the most colorful things you'll see on the Red Planet, says Lemon.
"I always marvel at the colors that appear: red, green, blue, violet... It's really nice to see something so bright with so many colors on Mars," he adds.