NASA’s Curiosity Rover Shows Colorful Clouds in the Sky of the Red Planet

In recent seasons on Mars, NASA’s Curiosity rover has regularly observed noctilucent clouds in the sky of the Red Planet and the play of colors on them in the rays of the setting sun. When scientists first saw colored spots in the pictures, they considered them to be an image defect. However, testing showed that at certain times of the day, Martian clouds are colored in red and green shades, bringing a little more life to the gloomy sky and desert landscapes of Mars.

Image source: NASA

There is an interesting situation with the observation of noctilucent clouds in the sky of Mars. It seems that they do not form everywhere and not at any time of the year. For example, the Perseverance rover, driving around the Jezero crater, has never observed this phenomenon in four Earth years on Mars. At the same time, the Curiosity rover, located south of the equator, regularly records noctilucent clouds. They were also previously observed by the NASA Pathfinder mission in 1997 in the northern hemisphere. Apparently, this phenomenon occurs in both hemispheres, but certainly not under all conditions.

Similar clouds also form on Earth, but on Mars they consist mainly of frozen carbon dioxide and only partly of water ice. Whereas terrestrial noctilucent clouds consist entirely of water ice. This specificity is noticeable when studying Martian clouds: they are located at an altitude of 60–80 km, and their plumes of frozen carbon dioxide can descend to 50 km, where they begin to evaporate. Observing their behavior gives an idea of ​​the size of the particles they consist of and the dynamics of the atmosphere as a whole. Color effects in the rays of the setting sun also provide valuable clues about processes in the atmosphere.

At the same time, scientists do not yet understand why noctilucent clouds are regularly visible in some places on Mars (for example, in the early spring season in the southern hemisphere, where Curiosity operates), and never in others. On this basis, a hypothesis has emerged that gravitational waves in the planet’s atmosphere may be responsible for the formation of noctilucent clouds on Mars. These are not the waves that occur when neutron stars and black holes collide, but the effect of Mars’ gravity on air masses. It is assumed that the zonal effect of gravity on cold carbon dioxide in the atmosphere leads to its supercooling, forcing it to condense into solid particles and form clouds.

While scientists try to unravel the nature of noctilucent clouds on Mars, we can only admire this rare phenomenon.