9.10.2025
Dust Devil, ESA
On Mars, dust devils and winds reach speeds of up to 160 km/h and are therefore faster than previously assumed: This shows a study by an international research team led by the University of Bern. The researchers analyzed images taken by the Bernese Mars camera CaSSIS and the stereo camera HRSC with the help of machine learning. The study provides a valuable data basis for a better understanding of atmospheric dynamics, which is important for better climate models and future Mars missions.
Despite the very thin Martian atmosphere, there are also winds on Mars that are central to the climate and the distribution of dust. The wind movements and the whirling up of dust also create so-called dust devils, rotating columns of dust and air that move across the surface. In images of Mars, the wind itself is invisible, but dust devils are clearly visible. Due to their movement, they are valuable indicators for researchers to determine the otherwise invisible winds.
A new study led by Dr. Valentin Bickel from the Center for Space and Habitability at the University of Bern shows that the dust devils and the winds that surround them reach significantly higher speeds than previously assumed. The stronger winds could be responsible for a large part of the dust uplift on Mars, which in turn has a major influence on the weather and climate of Mars. The study, in which researchers from the Department of Space Research and Planetology at the Physics Institute at the University of Bern, the Open University in the UK and the German Aerospace Center (DLR) are also involved, has just been published in the journal Science Advances.
Movement of dust devils studied with the help of deep learning
"Using a state-of-the-art deep learning approach, we were able to identify dust devils in over 50,000 satellite images," explains first author Valentin Bickel. The team used images from the Bern-based Mars camera CaSSIS (Color and Stereo Surface Imaging System) and the stereo camera HRSC (High Resolution Stereo Camera). CaSSIS is on board the European Space Agency’s (ESA) ExoMars Trace Gas Orbiter, while the HRSC camera is on board the ESA orbiter Mars Express. "Our study is therefore based exclusively on data from European Mars exploration," Bickel continues.
In a next step, the research team examined stereo images for around 300 of the identified dust devils in order to measure their directions of movement and velocities. Co-author Nicolas Thomas, under whose leadership the CaSSIS camera system was developed and built at the University of Bern and which is funded by SERI's Swiss Space Office through ESA's PRODEX program (see info box), explains: "Stereo images are images of the same spot on the surface of Mars, but taken a few seconds apart. These images can therefore be used to measure the movement of dust devils." Bickel emphasizes: "If you put the stereo images together in a sequence, you can observe how dynamically the dust devils move across the surface."
Winds on Mars stronger than previously assumed
The results show that the dust devils and the winds surrounding them on Mars can reach speeds of up to 44 m/s, i.e. around 160 km/h, across the entire planet, which is much faster than previously assumed (previous measurements on the surface had shown that winds mostly remain below 50 km/h and – in rare cases – can reach a maximum of 100 km/h). The high wind speed in turn influences the dust cycle on the Red Planet: "These strong, straight-line winds are very likely to bring a considerable amount of dust into the Martian atmosphere – much more than previously assumed," says Bickel. He continues: "Our data show where and when the winds on Mars seem to be strong enough to lift dust from the surface. This is the first time that such findings are available on a global scale for a period of around two decades."
Future Mars missions can benefit from the research results
The results obtained are also particularly important for future Mars missions. "A better understanding of the wind conditions on Mars is crucial for the planning and execution of future landed missions," explains Daniela Tirsch from the Institute of Space Research at the German Aerospace Center (DLR) and co-author of the study. "With the help of the new findings on wind dynamics, we can model the Martian atmosphere and the associated surface processes more precisely," Tirsch continues. These models are essential to better assess risks for future missions and adapt technical systems accordingly. The new study thus provides important findings for a number of research areas on Mars, such as research into the formation of dunes and slope streaks, as well as the creation of weather and climate models of Mars.
The researchers plan to further intensify the observations of dust devils and supplement the data obtained with targeted and coordinated observations of dust devils using CaSSIS and HRSC. "In the long term, our research should help to make the planning of Mars missions more efficient," concludes Bickel.
Quelle:
On Mars, dust devils and winds reach speeds of up to 160 km/h and are therefore faster than previously assumed: This shows a study by an international research team led by the University of Bern. The researchers analyzed images taken by the Bernese Mars camera CaSSIS and the stereo camera HRSC with the help of machine learning. The study provides a valuable data basis for a better understanding of atmospheric dynamics, which is important for better climate models and future Mars missions.
Despite the very thin Martian atmosphere, there are also winds on Mars that are central to the climate and the distribution of dust. The wind movements and the whirling up of dust also create so-called dust devils, rotating columns of dust and air that move across the surface. In images of Mars, the wind itself is invisible, but dust devils are clearly visible. Due to their movement, they are valuable indicators for researchers to determine the otherwise invisible winds.
A new study led by Dr. Valentin Bickel from the Center for Space and Habitability at the University of Bern shows that the dust devils and the winds that surround them reach significantly higher speeds than previously assumed. The stronger winds could be responsible for a large part of the dust uplift on Mars, which in turn has a major influence on the weather and climate of Mars. The study, in which researchers from the Department of Space Research and Planetology at the Physics Institute at the University of Bern, the Open University in the UK and the German Aerospace Center (DLR) are also involved, has just been published in the journal Science Advances.
Movement of dust devils studied with the help of deep learning
"Using a state-of-the-art deep learning approach, we were able to identify dust devils in over 50,000 satellite images," explains first author Valentin Bickel. The team used images from the Bern-based Mars camera CaSSIS (Color and Stereo Surface Imaging System) and the stereo camera HRSC (High Resolution Stereo Camera). CaSSIS is on board the European Space Agency’s (ESA) ExoMars Trace Gas Orbiter, while the HRSC camera is on board the ESA orbiter Mars Express. "Our study is therefore based exclusively on data from European Mars exploration," Bickel continues.
In a next step, the research team examined stereo images for around 300 of the identified dust devils in order to measure their directions of movement and velocities. Co-author Nicolas Thomas, under whose leadership the CaSSIS camera system was developed and built at the University of Bern and which is funded by SERI's Swiss Space Office through ESA's PRODEX program (see info box), explains: "Stereo images are images of the same spot on the surface of Mars, but taken a few seconds apart. These images can therefore be used to measure the movement of dust devils." Bickel emphasizes: "If you put the stereo images together in a sequence, you can observe how dynamically the dust devils move across the surface."
Winds on Mars stronger than previously assumed
The results show that the dust devils and the winds surrounding them on Mars can reach speeds of up to 44 m/s, i.e. around 160 km/h, across the entire planet, which is much faster than previously assumed (previous measurements on the surface had shown that winds mostly remain below 50 km/h and – in rare cases – can reach a maximum of 100 km/h). The high wind speed in turn influences the dust cycle on the Red Planet: "These strong, straight-line winds are very likely to bring a considerable amount of dust into the Martian atmosphere – much more than previously assumed," says Bickel. He continues: "Our data show where and when the winds on Mars seem to be strong enough to lift dust from the surface. This is the first time that such findings are available on a global scale for a period of around two decades."
Future Mars missions can benefit from the research results
The results obtained are also particularly important for future Mars missions. "A better understanding of the wind conditions on Mars is crucial for the planning and execution of future landed missions," explains Daniela Tirsch from the Institute of Space Research at the German Aerospace Center (DLR) and co-author of the study. "With the help of the new findings on wind dynamics, we can model the Martian atmosphere and the associated surface processes more precisely," Tirsch continues. These models are essential to better assess risks for future missions and adapt technical systems accordingly. The new study thus provides important findings for a number of research areas on Mars, such as research into the formation of dunes and slope streaks, as well as the creation of weather and climate models of Mars.
The researchers plan to further intensify the observations of dust devils and supplement the data obtained with targeted and coordinated observations of dust devils using CaSSIS and HRSC. "In the long term, our research should help to make the planning of Mars missions more efficient," concludes Bickel.
Quelle: University of Bern
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Dancing dust devils trace raging winds on Mars
In brief
Combing through 20 years of images from the European Space Agency’s Mars Express and ExoMarsTrace Gas Orbiter spacecraft, scientists have tracked 1039 tornado-like whirlwinds to reveal how dust is lifted into the air and swept around Mars’s surface.
Published today in Science Advances, their findings – including that the strongest winds on Mars blow much faster than we thought – give us a much clearer picture of the Red Planet’s weather and climate.
And with these ‘dust devils’ collected into a single public catalogue, this research is just the beginning. Besides pure science, it will be useful for planning future missions, for example incorporating provisions for the irksome dust that settles on the solar panels of our robotic rovers.
In-depth
We’ve been seeing dust devils for decades with Mars rovers and orbiters. This research takes a big step further, being the first to track the motion of so many of these twisters to find out how exactly they travel across Mars’s surface.
The study was led by Valentin Bickel from the University of Bern in Switzerland. Their catalogue is the first ever to include the speeds and directions of motions for dust devils all over Mars.
“Dust devils make the normally invisible wind visible,” explains Valentin. “By measuring their speed and direction of travel we have started mapping the wind all over Mars’s surface. This was impossible before because we didn’t have enough data to make this kind of measurement on a global scale.”
Mars is a dramatic planet, with vast volcanoes and cavernous craters. Why should we focus on something as seemingly dull as dust?
Dust can shield the Sun to keep daytime temperatures cooler, and act like a blanket to keep nighttime temperatures warmer. And particles of dust can act as the starting point for clouds to form, whilst dust storms can even force water vapour to escape into space.
Unlike on Earth, where it is washed out of the air by rain, dust can stay in Mars’s atmosphere for a long time, being blown all around the planet. So, for a better understanding of Mars’s climate, scientists are keen to understand when, where and how dust is lifted off the surface into the atmosphere.
More data, better picture
For this new study, researchers trained a neural network to recognise dust devils and then comb through images taken by Mars Express since 2004 and ExoMars TGO since 2016 to build up a catalogue of 1039 of them.
The map above shows the locations of all 1039 dust devils, and the direction of motion for 373. It confirms that although dust devils are found all over Mars, even on its towering volcanoes, lots are swept up from certain ‘source regions’. For example, many were clustered in Amazonis Planitia (upper left of the map), a huge patch of Mars covered in a fine layer of dust and sand.
By tracking how fast the dust devils moved, the researchers found wind speeds of up to 44 m/s, or 158 km/h. This is faster than we’ve ever measured with rovers on the ground – though it’s worth noting that the martian air is so thin that a human would barely even notice a wind of 100 km/h on Mars.
The researchers found that, in most cases, the dust devils were being blown across the landscape faster than our current Mars weather models predicted. In places where wind speeds are higher than expected, there may be more dust being lifted from the ground than we realised.
Like Earth, Mars has seasons. The catalogue also highlights that dust devils are most common in the spring and summer of each hemisphere. They last a few minutes and typically happen during the daytime, peaking between about 11:00 and 14:00 local solar time.
This is very similar to what we see on Earth, where dust devils are most common in dry and dusty places in the late morning to early afternoon during the summer months.
Better picture, safer exploration
This kind of big-picture view requires a lot of data, which can’t be captured by rovers and landers alone. Until now, our models of Mars’s climate have been based on the limited data we have from missions that don’t really cover much of the planet’s surface.
Thanks to this study, we now have lots of new measurements from all over Mars, helping to inform and refine the models. This improves our understanding and predictions of wind patterns around the Red Planet.
“Information on wind speeds and directions is also really important when planning the arrival of future landers and rovers at Mars,” mentions Valentin. “Our measurements could help scientists build up an understanding of wind conditions at a landing site before touchdown, which could help them estimate how much dust might settle on a rover’s solar panels – and therefore how often they should self-clean.”
We’re already using dust information to plan our future missions. Our ExoMars Rosalind Franklin rover is planned to touchdown on Mars in 2030 to avoid landing during the planet’s global dust storm season.
Valentin emphasises that “this catalogue of dust devil tracks is already public and anybody can use it for their own research. More entries are being added over time – Mars Express and ExoMars TGO are collecting new images every day.”
“Now that we know where dust devils usually happen, we can direct more images to those exact places and times. We are also coordinating the missions to image the same dust devils at the same time, to be able to compare the movement measurements and validate the data.”
From noise to gold
Mars Express and ExoMars TGO were never actually designed to measure wind speeds on Mars. Valentin’s team made use of a normally unwanted feature of the data to track the dust devils.
For both spacecraft, a single image is created by combining views from separate channels (each channel looks at Mars either in a specific colour or from a specific direction – or both). By design, there is a small delay between the views. This delay causes no problems as long as the surface is static, however it can cause slight ‘colour offsets’ in the final image whenever something is moving, such as clouds and dust devils. These offsets were exactly what the researchers were looking for – in Valentin’s words “we turned image noise into valuable scientific measurements”.
An imaging sequence from Mars Express combines up to nine image channels taken with a delay of about 7 to 19 seconds between each one. During these delays, any dust devil passing below moves a short distance, allowing the researchers to measure its speed. Because five separate image channels were used in this study, the team could even see how much the dust devil wobbled from left to right, as well as how its speed changed over time.
The GIF below shows a dust devil moving through the five channels in one Mars Express imaging sequence.
Images taken with ExoMars TGO’s Colour and Surface Stereo Imaging System (CaSSIS) combine two views taken either a second (for colour images) or 46 seconds (for stereo images) apart. Though we can’t see any wobble or acceleration, the extra delay lets us see dust devils moving much further between each image.
The first GIF below shows a dust devil photographed by ExoMars TGO with a one-second delay between views. The second GIF shows the same dust devil imaged with a 46-second delay.
“It’s great to see researchers using Mars Express and ExoMars TGO for totally unexpected research,” says Colin Wilson, ESA project scientist for both missions. “Dust affects everything on Mars – from local weather conditions to how well we can take images from orbit. It’s difficult to understate the importance of the dust cycle.”
Quelle: ESA