Using images captured by the European Space Agency’s Mars Express spacecraft, researchers have created a cloud atlas of Mars, to better understand the climate of the Red Planet.
The most complete catalogue of clouds found on Mars has revealed the planet’s dazzling array of atmospheric phenomena, including some unlike any seen on Earth.
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| Orographic clouds form near volcanoes ESA/DLR/FU Berlin/A. Cowart |
Mars’s atmosphere is thin and made up of primarily carbon dioxide. When condensed by cool temperatures and mixed together with dust and water vapour, it can create striking cloud patterns.
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| Elongated dust clouds aren’t found on Earth ESA/DLR/FU Berlin/A. Cowart |
To better understand these patterns and their impact on Mars’s climate, Daniela Tirsch at the German Aerospace Center in Berlin and her colleagues have collected images of them in a “cloud atlas”. The pictures, taken from a camera on the European Space Agency’s Mars Express probe, span more than 20 years since the spacecraft first arrived at the planet in 2003.
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| Gravity wave clouds on Mars ESA/DLR/FU Berlin/A. Cowart |
Some of the clouds are similar to those we see on Earth. These include gravity wave clouds, which look like thin, stretched-out strands of hair and are caused by features on the land below forcing parts of the atmosphere upwards, making them interact with other columns of atmospheric gas. Then there are cloud streets, which look similar, but are spread out over larger regions and are instead caused by chaotic currents in Mars’s atmosphere. “They are enigmatic but beautiful,” Tirsch told the Europlanet Science Congress in Berlin on 9 September.
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| Cloud streets are “enigmatic but beautiful” ESA/DLR/FU Berlin/A. Cowart |
Other clouds are a result of Mars’s atmospheric conditions and have no Earth analogues, such as elongated dust clouds (see top of article). As their name suggests, these contain vast quantities of Martian dust. Elongated dust clouds can extend for hundreds of kilometres and have a striking red hue.
There are also clouds that form from unique Martian features, such as orographic clouds, which form when the planet’s towering mountains and volcanoes force large amounts of gas upwards. Some of these clouds can also mix with dust or dust-filled storms to create features that look like eruptions, even though Mars is largely geologically inactive.
Clouds that only form at certain times of day, such as twilight clouds, which appear near the horizon as the sun rises on Mars, are particularly perplexing. These can take on very different forms, from ones similar to the cirrus clouds seen on Earth to strange blobby clouds clustered together. “We were astonished at the wealth of morphologies that twilight clouds could have,” said Tirsch.