For the fourth year in a row, NASA’s Curiosity rover has photographed iridescent clouds drifting across the Martian sky. The clouds appear in the same place, at the same time of year.
On January 17, during the early Martian autumn, Curiosity’s Mastcam recorded these noctilucent, or “night-shining,” clouds for 16 minutes. The Sun’s rays scatter against the clouds, creating colorful, “mother-of-pearl” clouds tinged with red and green.
Cloudgazing… on Mars! ☁️
@MarsCuriosity captured these colorful clouds drifting across the Martian sky. The iridescent, carbon dioxide ice formations offer clues about Mars’ atmosphere and weather: https://t.co/HAp2FDFjhk pic.twitter.com/DEWV477X01— NASA (@NASA) February 11, 2025
Dry ice clouds
Regular Martian clouds are composed of water ice, but researchers believe that frozen carbon dioxide, or dry ice, makes up the noctilucent clouds. They float 60 to 80 kilometers above the surface of the Red Planet, where frigid temperatures cause the carbon dioxide to condense into colorful, wispy clouds. Some plumes descend to 50 kilometers before evaporating in the rising temperatures.
Photo: NASA/JPL-Caltech/MSSS/SSI
Twilight clouds on Mars were first observed during NASA’s Pathfinder mission in 1997. Curiosity’s recent observations mark the fourth time that these iridescent clouds have appeared over the Gale Crater in the planet’s southern hemisphere. They seem to come at the same time each year.
Noctilucent clouds on Mars seen by NASA’s Curiosity Mars rover, May 17, 2019. Photo: NASA/JPL-Caltech
This predictability has allowed scientists to plan their observations meticulously. Mark Lemmon, an atmospheric scientist at the Space Science Institute, recalls his initial encounter with these clouds: “At first, [I was sure] it was some color artifact…Now it’s become so predictable that we can plan our shots in advance.”
NASA’s Curiosity Mars rover spotted these mother-of-pearl clouds on March 5, 2021. Photo: NASA/JPL-Caltech/MSSS
Strangely, the twilight clouds do not seem to form anywhere else on the planet. One hypothesis is that atmospheric gravity waves help generate the clouds. The waves cool the atmosphere and create cool enough conditions for the clouds to form.
This is, however, just a theory. “Martian gravity waves are not fully understood and we’re not entirely sure what is causing twilight clouds to form in one place but not another,” says Lemmon.
Clouds drifting over Mount Sharp on Mars, as viewed by NASA’s Curiosity rover on March 19, 2021. Credit: NASA/JPL-Caltech/MSSS
