Twilight and Dust Clouds Fill Mars’ Atmosphere

Mars, Earth’s closest planetary neighbor, has long fascinated scientists who have been exploring it for potential signs of life and the possibility of future human habitation. A recent study has revealed stunning cloud patterns that appear on the red planet.

Since 2005, the High-Resolution Stereo Camera (HRSC) aboard the European Space Agency’s (ESA) Mars Express spacecraft has been capturing images of clouds on Mars. This vast collection of cloud imagery spans over 20 years.

The resulting “cloud atlas,” compiled by Daniela Tirsch and her team at the German Aerospace Center in Berlin, showcases the mesmerizing atmospheric phenomena found on Mars. While some clouds resemble those on Earth, others are entirely unique to the Martian atmosphere.

These clouds form when Mars’ thin atmosphere, primarily composed of carbon dioxide, interacts with dust and water vapor. “Clouds on Mars are as varied and captivating as those on Earth, with some features unique to the red planet,” Tirsch explained.

Among the clouds that resemble Earth’s are gravity wave clouds. These delicate formations occur when surface features push parts of the atmosphere upward, causing interactions with other atmospheric gases. Another familiar formation, cloud streets, spread across large areas and resemble gravity wave clouds but are formed by turbulent air currents in Mars’ atmosphere. Tirsch, speaking at the Europlanet Science Congress in Berlin, described them as “enigmatic but beautiful.”

One of her favorite phenomena is the “cloud streets”—rows of fluffy clouds that form around Mars’ vast volcanic region, Tharsis, and the northern lowlands during the planet’s spring and summer seasons. Though similar to Earth’s cumulus clouds, these Martian clouds form under entirely different conditions.

Mars also hosts clouds unlike any found on Earth, such as massive dust clouds, which are bright red due to Martian dust and can stretch for hundreds of kilometers. “We also witness impressive dust clouds that spread over vast distances—a phenomenon we are fortunate not to experience on Earth,” said Tirsch.

The planet’s unique features, such as its towering volcanoes, give rise to orographic clouds. These clouds form when large amounts of gas are forced upward near the volcanoes. They can sometimes mix with dust or dust storms, creating clouds that resemble volcanic eruptions.

Twilight clouds particularly amazed researchers. “We were astonished at the diversity of shapes that twilight clouds could take,” Tirsch shared. These clouds form near the horizon as the sun rises on Mars, creating an array of stunning appearances.