Though the Martian atmosphere is only one percent as dense as the Earth's, it's strong enough to generate intense winds. What's more, the planet has dust in spades, and its wide, wind-swept plains make the perfect breeding ground for so-called "dust devils."
Like dust devils on Earth, the Martian ones are essentially miniature tornadoes of dust kicked up by the wind. They're pretty frequent on Mars, but as scientist Sharon Wilson says, rarely are they captured by cameras.
Fortunately, the Mars Reconnaissance Orbiter (MRO) happened to be in the right place at the right time recently, and the spacecraft's HiRise camera captured footage of a dust devil, spinning around and dancing across the landscape of the Amazonis Planitia, 250 or so miles below.
Wilson estimates, based on the length of the shadow cast by the storm, that its clouds reached about 2,100 feet into the Martian atmosphere. By comparison, a tornado on Earth can reach up to 45,000 feet into the atmosphere. The width of the storm is estimated to be about 164 feet across; a small (F1) Earth-bound tornado can be 36-165 feet across.
This is not the first time a spacecraft on or near Mars has captured such a storm. Back in 2016, as CNET reported at the time, the Opportunity Rover, which unlike the MRO is on the ground on Mars, captured a dust devil off in the distance. As an added bonus, the craft's camera picked up its own tire tracks in the image.Though impressive to look at from hundreds of millions of miles away, Martian dust devils may yet bedevil human beings. That's because any humans that step onto the surface of the planet -- if and when that ever happens -- would be in grave danger should they be on the wrong end of one. Similarly, the spacecraft that they occupy as their home could be damaged by one as well. Specifically, the dust devils generate static electricity, effectively putting humans and spacecraft at risk of "towering electrified dust devils," as NASA warns.
Meanwhile, another dust-related problem on Mars could not only jeopardize human exploration of the Red Planet, but it has already wreaked havoc on scientific equipment that's already up there. Mars is so dusty that planet-wide dust storms are known to kick up from time to time, and they can last for months. A 2018 Martian dust storm knocked the Opportunity offline as dust covered its solar panels, robbing it of sunlight to convert to battery power.