Nearly 50 years ago, NASA’s twin Viking orbiters captured images of narrow, twisty columns of dust swirling their way across the Martian surface. The shadowy figures were later confirmed to be dust devils, one of the most fascinating weather phenomena ever observed on Mars. In a new study, scientists combined 20 years’ worth of data on dust devils captured by two orbiters currently circling the Red Planet, revealing that Mars’ winds blow at much faster speeds than originally thought.
The study, published this week in Science Advances, combines images by the European Space Agency’s Mars Express and ExoMars Trace Gas Orbiter spacecraft. Scientists analyzed a total of 1,039 dust devils across different parts of Mars, measuring how they traveled along the planet’s surface. They found that winds move as fast as 99 miles per hour (160 kilometers per hour).
“Dust devils make the normally invisible wind visible,” Valentin Bickel, a researcher at the University of Bern in Switzerland, and lead author of the study, said in a statement. “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.”
The devil is in the details
Dust devils form when the planet’s surface heats up, pushing hot air close to the ground rapidly up through cooler air above. As the warm air rises, it creates a pocket which the cooler air then rushes in to fill the void, causing a rapidly rotating column of wind.
Dust tends to hang around in the Martian atmosphere. By learning how dust gets lifted off the surface and into Mars’ atmosphere, scientist could glean a better understanding of the planet’s climate.
The researchers composed a map showing the location of all the dust devils recorded by ESA’s orbiters, and the direction of motion for 373 of them. Although dust devils form all over Mars, the new study found that there were a few hotspots where they originated more frequently.
The researchers behind the new study also found that the dust devils were blowing across Mars’ landscape much faster than other weather models had predicted. In areas where Mars’ winds move faster, there appears to be more dust being lifted up into the atmosphere.
By cataloging hundreds of dust devils over the years, the researchers also noticed that the phenomenon occurs more frequently during Mars’ spring and summer time, and that they typically form during the day between the hours of 11 a.m. and 2 p.m. solar time.
“Now that we know where dust devils usually happen, we can direct more images to those exact places and times,” Valentin said. “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.”
The data may also prove valuable to future human missions to the Red Planet. “Information on wind speeds and directions is also really important when planning the arrival of future landers and rovers at Mars,” Valentin added. “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.”