Iridescent cloud

Rover photographs “rainbow feather” on Mars

(Bild: NASA/JPL-Caltech/MSSS)

The "Curiosity" rover has taken a highly fascinating photo on Mars. The photo published on the website of the US space agency shows an iridescent cloud, whose shape is strikingly reminiscent of a feather, shortly after sunset.

The image (see above) was taken on January 27, 2023 as part of the Twilight Cloud Survey research mission, during which clouds on Mars were examined at dusk with the help of Curiosity. The colors of iridescent clouds tell scientists something about the particle size in the clouds and how they develop over time.

Twilight clouds were first sighted on Mars in 1997 as part of NASA's "Pathfinder" mission. "Curiosity" only discovered them in 2019, when it took the first images of iridescent clouds - a phenomenon that occurs in early fall in the southern hemisphere of the Red Planet.

A big mystery is why the twilight clouds of carbon dioxide ice have not been spotted elsewhere on Mars. "Curiosity, which landed in 2012, is located on Mount Sharp in Gale Crater, just south of the Martian equator. "Pathfinder" landed in Ares Vallis, north of the equator.

"Curiosity" (pictured) has been searching for traces of past life on Mars since 2012.

(Bild: NASA/JPL-Caltech/MSSS)

Do gravity waves form these clouds?
Mark Lemmon, an expert in atmospheric research at the Space Science Institute in Boulder (Colorado), and others suspect that certain regions of Mars may be predisposed to form such clouds. One possible source could be gravity waves that can cool the atmosphere, he said.

"Carbon dioxide (CO₂) was not expected to condense into ice here. Something is cooling the atmosphere enough for that to happen. However, the gravity waves on Mars are not yet fully understood, so we're not entirely sure what causes twilight clouds to form in one place and not in another," says Lemmon.

Rover on Mars since 2012
"Curiosity" landed on Mars in August 2012 and is searching for traces of past life. At almost 900 kilograms and three by 2.7 meters, it was the largest self-propelled research robot ever sent to the Red Planet until the landing of the "Perseverance" rover.