NASA’s Curiosity rover captured beams of light illuminating a bank of clouds. Known as twilight rays, these sun rays have been so clearly observed on Mars.

Curiosity captured the view as the sun dipped below the horizon on Feb. 2. The photo was taken by Curiosity during the rover’s most recent study of twilight clouds, which builds on its 2021 observations of noctilucent or noctilucent clouds.

The clouds in the most recent images appear to be at a higher altitude, where it is very cold, but most Martian clouds are made of water ice and do not hang more than 60 kilometers above the surface. This suggests that dry ice, or carbon dioxide ice, makes up these clouds.

Scientists can gain additional knowledge about the composition, temperatures and winds of the Martian atmosphere by observing when and where clouds form. Each panorama that Curiosity captured of the sun’s rays and iridescent clouds was created by stitching together 28 images that were sent to Earth. The photos have been adjusted to draw attention to the highlights.

More black-and-white navigation camera data from Curiosity was used in the 2021 cloud survey to take an in-depth look at the structure of a cloud as it moves. Nevertheless, the most recent research, which began in January and will end in mid-March, relies primarily on the Mastcam, a color camera mounted atop the rover that allows scientists to observe how cloud particles evolve over time.

Curiosity looks at feather-shaped iridescent cloud
Curiosity Views Pinnate Iridescent Cloud: This pinnate iridescent cloud was captured just after sunset on January 27, 2023, the 3,724th Martian or solar day of Curiosity’s mission. Credits: NASA/JPL-Caltech/MSSS.

In addition to the image of sunbeams, Curiosity captured a series of colorful feather-shaped clouds on Jan. 27. When illuminated by sunlight, certain types of clouds can create a rainbow-like display called iridescence.

Mark Lemmon, an atmospheric scientist at the Space Science Institute in Boulder, Colorado, said: “When we see iridescence, it means that the particle size of a cloud is identical to their neighbors in every part of the cloud. By looking at color transitions, we see the particle size change throughout the cloud. That tells us about the way how the cloud evolves and how the particles change size over time.”