The Devil is in the details

By Phil Plait | September 29, 2005 9:31 pm

The other day I was in the car with Mrs. Bad Astronomer, and while we were stopped at a light she suddenly pointed out the window and shouted, “Dust devil!”

I took a look, and sure enough, there was a little swirl of wind circling around in front of the car. It was about a foot across, and had picked up some leaves and detritus, whirling around like a miniature and delicate tornado.

Dust devils are in fact similar to tornados, but are not nearly so violent. I’ve seen lots of them, from small ones that can barely pick up leaves, to a big one once when I was in college. That one had formed — I think — due to the unusual shape of a building. Wind would come around the building, create a vortex, and was fed by warm air in the surrounding field. It was easily two or three meters across, and maybe 15 meters high. I watched it for quite a while, 10 or 15 minutes at least, as it would wander away from the building, wander back, pick up leaves, fling them around. It was fascinating!

It’s been known for a while that dust devils are not restricted to Earth. Mars is blighted with them.

Orbiting spacecraft show the view from a height. In the image above, we are looking straight down on a few of the devils. You can see their shadows above them! There are countless images like this one. As the funnel sucks up the sand beneath them, they leave the darker rock exposed, and so many images show winding, spiraling dark trails across the martian surface.

Then we landed rovers on the surface! Suddenly, dust devils got even more interesting, because we could see them from the side. Here’s an image from one of the rovers:

Not only that, but multiple images could be taken, and made into animations. You can watch them move! Atmospheric Scientist Mark Lemmon at Texas A&M University shares my fascination with these beasties, but he has access to the data, and the tools to make the data even cooler. On his website he has collected dozens of these events, and has created very cool animations from them.

By watching those movies, you are seeing weather on another planet.

Do I even have to say it? Science is so cool!


Comments (20)

Links to this Post

  1. Pharyngula | September 30, 2005
  1. CR

    A few years ago, I saw video footage of a dust devil on Earth that was lifting a bunch of freshly cut hay into the sky, partially with the help of a group of kids who were having a fun time tossing the hay into the air to see how far the wind would carry it aloft. I’ve since seen stills from this footage, and the name “haynado” was coined to refer to it.
    Just two weeks ago, I was driving alongside a cornfield that had recently been harvested, and saw a similar effect with corn leaves and stalk fragments. Unfortunately, I couldn’t stop to watch the “cornado” as I called it, nor did I have a camera along to snap a photo. :-(
    As for Mars’ dust devils, for some time now, I’ve been telling people I know about “weather on another planet” and how exciting that is. Thanks for posting the links!

  2. Berkeley

    Did anyone see the latest Mars weather forecast? I know it is out there (on the web somewhere), but I’m not able to find it.

  3. Richard Board

    Berkeley: There are a number of sites which publish Mars weather (and other data). A browser search will reveal several. One of my favorites is Enjoy. Also, Martian rovers site at NASA is especially helpful in keeping up with news about our beautiful red companion.

  4. What amazes me is that they spent months earlier in the mission, particularly when Spirit was enroute to the Columbia Hills, desperately trying to get dust devil images without success. Now there’s scarcely a set of images taken that doesn’t include at least one and frequently more.

  5. Evolving Squid

    I’ve not kept up on the latest woo-woo news yet, but has anyone tried to draw a weird connection like “dust devils actually live Martians” or some crud like that? Might make a humourous read… in a pathetic, kind of sad way.

    For my part, I think it’s just plain cool. I remember watching the first moon landing (it was my 4th birthday, by coincidence)… and now we have movies of weather on the surface of other planets.

    I’ve often wondered how much life we’re seeding on other planets, though, particularly Mars. I know NASA takes considerable pain to ensure the things they fling at other planets are sterile, but let’s face it, there’s no POSSIBLE way the stuff is going to be 100% sterile. I’m positive there’s bacteria that could survive the voyage, and maybe even the conditions on Mars (or Titan, or wherever). I wonder if, perhaps, we’ve already made some Martians inadvertently? What are our ethical and moral responsibilities in that regard?

  6. Kevin

    Isn’t the current theory on why the rovers have lasted so long is the martian dust devils are cleaning the dust off the solar collectors?

  7. TheBlackCat

    Evolving Squid, the “dust devil alien” idea is actually kind of ironic, considering people in the Middle East used to believe a race called the Djinn or Jinn, (called “genies” in the west) use dust devils to travel in the desert here on Earth. So considering how old myth tend to be recycled, I don’t see your worry being too far-fetched.

  8. Nigel Depledge

    Evolving Squid – while I think you’re right in principle (that there is no way to be 100.0000% sure the rovers were sterile when they landed), I think there is a good chance that they did not take viable organisms onto the surface with them. Space vehicles are usually assembled in a clean room environment (I would guess they use the standard of either 10,000 or 100,000, the figure being the maximum number of particles per cubic foot of air), and Spirit and Opportunity spent several months being exposed to the solar wind. Granted, the flux of the solar wind at any particular point in space may not be very high, but with that duration of exposure it would be unlikely for bacteria to survive unless the bugs were paticularly radiation-tolerant (or maybe they got super powers …?) or particularly well shielded.

    I’ve never seen a dust devil of any significant size, but I’ve seen the equivalent on a lake : spindrift. Quite spectacular.

  9. Martin

    Is it correct to say that dust devils are similar to tornados? They are similar in that they are rotating columns of air, but the method of formation is entirely different. The dust devil is created by rising warm air which begins to turn because of the Coriolis Effect, and is generated from the ground up. The tornado is generated high in the atmosphere through the confluence of warm moist air, warm dry air and cool air and is generated from the top down.

  10. In the USA southwest, dust devils can be several hundred meters across and a few thousand high. I’ve been in dust well above 10,000′ above ground in a sailplane.

    The devils are too small to be affected by coriolis, so just like water in the drain, go whichever direction they feel like.

    Visit for more information on sailplanes and what keeps them up.


  11. badger3k

    I was in Saudi during the first gulf war and had the “honor” of getting caught in one. Just walking in camp, luckily wearing my goggles at the time, and I was suddenly caught in wind and sand. It was gone in a moment, but I turned around and saw the dust devil whirling away from me. Definitely interesting.

  12. Evolving Squid

    >>Visit for more information on sailplanes
    >>and what keeps them up.

    Intelligent Falling keeps them up :)

  13. Andrew

    In Australia they’re called willi-willis – apparently from an Aboriginal word. They are very frequent out in the windy semi-arid area I grew up in (Coleambally) but they are rarely more than about 15 metres high..

  14. Evolving Squid

    If you go to right now, they have a video clip of a relatively unpleasant little spud starting up in the middle of a soccer game and tossing some stuff around. It’s pretty cool.

  15. JusANuttaBackYahdah

    Yes BA science is cool and fun!
    To Evolving Squid, love your take on things.
    To Kevin, it ain’t the dust devils keeping the the rovers going but those little green guys inside of the devils with their feather dusters cleaning the solar panels and greasing the wheels.

    Clear skies (devils not withstanding) ūüėČ

  16. Just read this new article on the mechanism for dust devils:

  17. You might enjoy a short video I made while chasing dust devils on El Mirage Dry Lake in Southern Cal, you can check it you here:

  18. Freddybaby

    Did anyone else catch the reflections (or whatever) in the last few frames of the dust devil animation ? Looks like it could possibly be a spin off vortex ???

    I spend a week or so every August in the black rock desert, we LOVE dust devils, and fire devils too.. Imagine a vortex of flames about 75-300ft high peeling into the dark, it’s amazing…

  19. A

    For the benefit of dust-devil lovers everywhere, someone should mention R.A. Heinlein’s “Our Fair City”, a good, short read featuring Kitty: a whirlwind with a great personality.


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