Image of a dust devil, a whirlwind of dust that is blown across Mars’ surface. Credit: ©ESA/TGO/CaSSIS/DLR/FUBerlin
Mars is home to a very thin atmosphere, with a volume less than 1% of Earth’s. Despite this, scientists have observed intense Martian winds and dust storms.
A new study, published in Science Advances, has photographed dust collected by the winds into ‘dust devils’ – rotating columns of dust and air that move across the planet’s surface.
The new research offers a clearer understanding of Mars’s climate and dust cycle, which will play an important role in planning future missions to the Red Planet.
“Dust devils make the normally invisible wind visible,” says Valentin Bickel, the first author of the study from the University of Bern, Switzerland.
“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.”
Bickel and the team measured the speed of the dust devils by analysing satellite images of the planet’s surface from the High Resolution Stereo Camera (HRSC) on board the European Space Agency’s (ESA) orbiter Mars Express, and the Colour and Stereo Surface Imaging System (CaSSIS) on ESA’s ExoMars Trace Gas Orbiter.
“Stereo images are images of the same spot on the surface of Mars, but taken a few seconds apart,” says co-author Nicolas Thomas from the University of Bern, who helped develop the CaSSIS camera system.
“These images can therefore be used to measure the movement of dust devils.”
The team identified and verified 384 dust devils from the CaSSIS images and 655 from the HRSC images.
While the dust devils were found across all of Mars, they were more likely to be found in dry places during the summer and spring months. They typically only lasted a few minutes, peaking between 11:00 and 14:00 local solar time.
“Now that we know where dust devils usually happen, we can direct more images to those exact places and times,” says Bickel.
“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.”
When the researchers analysed the images, they found the dust devils and surrounding winds reached speeds of up to 158km/h (44m/s). Previous studies had suggested that winds on Mars mostly remain below 50km/h, reaching up to a maximum of 100km/h on rare occasions.
“Our data show where and when the winds on Mars seem to be strong enough to lift dust from the surface,” says Bickel.
“This is the first time that such findings are available on a global scale for a period of around 2 decades.”
The researchers hope that their study will help inform climate and weather models for the planet which will be crucial for future Mars missions. In particular, the findings will significantly influence Martian atmosphere models.
“With the help of the new findings on wind dynamics, we can model the Martian atmosphere and the associated surface processes more precisely,” says co-author Daniela Tirsch from the Institute of Space Research at the German Aerospace Centre.
“A better understanding of the wind conditions on Mars is crucial for the planning and execution of future landed missions.”
The study also informs scientists on how dunes and slope streaks may have formed on Mars.
“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,” says Bickel.
“In the long term, our research should help to make the planning of Mars missions more efficient.”