There’s no way to sugarcoat it: Mars has a “dust problem.” The surface of the Red Planet is covered in particulate matter consisting of tiny bits of silica and oxidized minerals. During a Martian summer in the southern hemisphere, the planet experiences dust storms that can grow to encompass the entire planet. At other times of the year, dust devils and dusty skies are a persistent problem. This hazard has claimed robotic explorers that rely on solar panels to charge their batteries, like NASA’s Opportunity rover and the InSight lander, which ended their missions in 2018 and 2022, respectively.
Martian dust has also been a persistent challenge for the Ingenuity helicopter, the rotorcraft that has been exploring Mars alongside NASA’s Perseverance rover since February 2021. Luckily, the way it has kicked up dust has provided vital data that could prove invaluable for rotorcraft sent to explore other extraterrestrial environments in the future. Using this data, a team of researchers (with support from NASA) has completed the first real-world study of Martian dust dynamics, which will support missions to Mars and Titan (Saturn’s largest moon) in this and the next decade.
The study was led by Mark T. Lemmon, a senior research scientist at the Space Science Institute’s (SSI) Center for Mars Science in Boulder, Colorado. He was joined by researchers from the Stevens Institute of Technology, the Johns Hopkins University Applied Physics Laboratory (JHUAPL), Aeolis Research, Cornell University, Arizona State University, the Centro de Astrobiologia (INTA-CSIC), and NASA’s Jet Propulsion Laboratory. The paper that describes their analysis recently appeared in the Journal of Geophysical Research: Planets.
Studying dust dynamics on another planet is difficult, given the distances and communications delays involved. As a result, researchers rely on Computational Fluid Dynamics (CFD) to simulate how dust behaves in extraterrestrial environments based on the local conditions. Said Jason Rabinovitch, an assistant professor at the Stevens Institute of Technology and a co-author on the study:
“There’s a reason that helicopter pilots on Earth prefer to land on helipads. When a helicopter lands in the desert, its downdraft can stir up enough dust to cause a zero-visibility ‘brownout’ – and Mars is effectively one big desert. Space is a data-poor environment. It’s hard to send videos and images back to Earth, so we have to work with what we can get.”
The Rabinovitch Research Group at Stevens investigates plume-surface interactions during the powered descent of spacecraft. They also model supersonic parachute inflation, small satellite hybrid rocket propulsion, and geophysical phenomena. This includes “yardangs,” a feature found on Earth and Mars where protruding rocks are carved by the dual action of wind abrasion by dust and sand and the removal of loose material by wind turbulence (deflation). Rabinovitch has been working with NASA JPL and the Ingenuity program since 2014, creating the first theoretical models of dust kicked up by helicopters on Mars.
For the sake of their study, Rabinovich and his teammates used advanced image-processing techniques to extract information from the low-resolution videos of Ingenuity‘s six helicopter flights captured by Perseverance. By identifying tiny variations between video frames and the light intensity of individual pixels, Rabinovich and his colleagues calculated the size and mass of dust clouds the helicopter kicked up during takeoff, hovering, and landing. The results were strikingly similar to the models he and his colleagues created in 2014.
Specifically, they estimate that Ingenuity kicked up about one-thousandth of its own mass (1.8 kg; 4 lbs) each time it flew. This is many times more dust than a rotorcraft of similar mass would generate here on Earth, a result of Martian gravity being roughly 40% that of Earth’s and atmosphere pressure being less than half of a percent. However, given the remaining uncertainties, Rabinovich and his teammates are cautious about making direct comparisons.
“When you think about dust on Mars, you have to consider not just the lower gravity, but also the effects of air pressure, temperature, air density – there’s a lot we don’t yet fully understand,” he said. Nevertheless, the fact that there is still much to be learned is part of what makes the research so interesting. “It was exciting to see the Mastcam-Z video from Perseverance, which was taken for engineering reasons, ended up showing Ingenuity lifting so much dust from the surface that it opened a new line of research,” added Lemmon.
This research will lead to a better understanding of Martian dust storms, which would help NASA extend future missions that rely on solar power. It could also help with Entry, Descent, and Landing (EDL) techniques whenever sensitive equipment needs to land on Mars’ dusty surface – like the NASA/ESA Mars Sample Return (MSR) mission. It could also lead to a better understanding of the role dust storms play in meteorological phenomena that Earth and Mars share.
This will also prove useful for mission planners working on NASA’s Dragonfly mission, a nuclear-powered quadcopter that will launch towards Titan (Saturn’s largest moon) by 2027. For any celestial bodies that have atmospheres, wind-borne erosion, and plenty of particulate matter on their surfaces, these types of studies will be invaluable when it comes time to prep missions to explore them.