A fascinating sight has been captured by NASA’s Curiosity rover – a feather-shaped cloud glowing in the Martian sky, shortly after sunset on the Red Planet.

This image, which dates back to January 2023, was recently highlighted by NASA in a feature on the rover’s investigation of the planet’s skies, which took place last month.

During this investigation, Curiosity took images over a period of 16 minutes on January 17, or Sol 4426 on Mars, showing reddish-green clouds in the Martian twilight. These clouds are known as noctilucent, or “night shining” clouds, which occur due to the way the Sun’s light scatters in the dusty Martian atmosphere.

As noted in a NASA release, Martian clouds are composed of either water ice or carbon dioxide ice, with the latter type, which occurs at higher altitudes and lower temperatures, being the ones that shine in the observed manner. Noctilucent clouds on Mars are typically found at altitudes between 37 and 50 miles (60 and 80 kilometers) above the surface, and they evaporate when they drift lower than 31 miles (50 kilometers) due to rising temperatures in the atmosphere.

Noctilucent clouds are not unique to Mars; they can also be caused on Earth by rocket launches, which can create glowing clouds in the upper atmosphere that are only visible shortly after sunset or before sunrise.

Mars’ clouds come in a variety of shapes and sizes. In 2022, scientists from the ESA spotted clouds similar to those found on Earth in the Martian skies. The following year, the Perseverance rover encountered heavy cloud cover, indicative of the overcast days that were to come on the dusty planet. Although the recently imaged iridescent clouds are not a new discovery, they remain mesmerizing and require further study.

The first sighting of twilight clouds on Mars was made by NASA’s Pathfinder mission in 1997, and Curiosity first captured them in 2017. Last month’s sighting marks the fourth Mars year that the rover has observed these clouds.

Late last year, NASA researchers published a study in the Geophysical Research Letters, detailing how the iridescent effect provides insight into the formation and growth of ice in Mars’ atmosphere.

Mark Lemmon, an atmospheric scientist at the Space Science Institute in Colorado and the lead author of the study, recalled in a NASA release, “I’ll always remember the first time I saw those iridescent clouds and thought it was a color artifact. Now, it’s become so predictable that we can plan our shots in advance; the clouds appear at exactly the same time every year.”

According to the release, these clouds have not been observed by rovers in other parts of Mars, suggesting that the region Curiosity is exploring, specifically Gale Crater’s Mount Sharp, may be particularly conducive to hosting these clouds.