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Space Science

NASA Reveals Dust Devil Data from Mars 116

Posted by CowboyNeal
from the round-and-round dept.
saskboy writes "NASA reports that Martian dust devils could be much more destructive than previously considered. You may remember this past April when it was revealed that whirlwinds actually helped the current rovers by cleaning accumulated dust from their solar cells which increased their energy collection efficiency. But after studying the mini-storms more, they realize that the dust and sand particles could cause static electricity discharges, also known as lightning. The high speed grains of sand blowing around at about 30 meters/second (70 miles per hour) are nothing to blink at either, since they can damage astronauts or equipment on the Martian surface. The height of a Martian dust devil can reach 10km (6 miles), which means it's more like the size of a terran tornado."
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NASA Reveals Dust Devil Data from Mars

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  • A quick question (Score:4, Insightful)

    by zegebbers (751020) on Saturday July 16, 2005 @09:37AM (#13080865) Homepage
    From the blurb : "The height of a Martian dust devil can reach 10km (6 miles), which means it's more like the size of a terran tornado."

    Does that mean that a tornado is only on earth? Why are these referred to as "Dust Devils" and not tornadoes generally? Cheers

    • Re:A quick question (Score:3, Interesting)

      by i8a4re (594587)
      My guess is that tornados form from storm clouds where dust devils form due to convection from heating. While they are both vorticies, their origin is what distinguishes them.
      • Re:A quick question (Score:3, Informative)

        by TykeClone (668449) *
        I'd guess that it's the amount of (destructive) power that differentiates between the two.

        Both tornados and dust devils happen when the air close to the ground is warmer than the air up a bit higher. In tornados, there is a lot more power generated over a larger area (and has the potential to do more damage) than a dust devil would.

        Because of the thin martian air, the dust devils have little destructive power so they aren't called tornados.

        • I'd guess that it's the amount of (destructive) power that differentiates between the two.
          I'd guess so too. And apparently, 70 mph does qualify, albeit in the very weakest category of tornadoes [infoplease.com]:

          F0 light 40-72 mph
          F1 moderate 73-112 mph
          F2 significant 113-157 mph
          F3 severe 158-206 mph
          F4 devastating 207-260 mph
          F5 incredible 261-318 mph

      • They both form from convection.

        When the sun heats the ground, the air next to the ground gets hot, expands, becomes less dense than unheated air, becomes buoyant, and rises. Air from less heated ground areas (cultivated fields, for instance) flows radially in to replace the air rising from hotspots (like rocky areas), and owing to some rather complex mathematical considerations, comes in in a spiral path. The air rising from the hotter spots is called a thermal. Buzzards circle in them to stay aloft and hu
    • Does that mean that a tornado is only on earth?

      No, although Tornadoes may only be found on Earth (I highly doubt it), tyhe fact it's called a dust devil doesn't mean Tornadoes are only found on Earth. It would have been compared with a Tornado, because it's is comparable to a tornado in size only (and most people would have an idea as to what the size would be).
    • Re:A quick question (Score:1, Interesting)

      by Anonymous Coward
      A tornado is a vortex that by definition has to be in contact with both the ground and a cloud base. The Martian vortex under discussion forms in a cloudless environment, therefor it shouldn't be called a tornado. Furthermore, the mechanism that creates and sustains the Martian devils appears to be identical to the mechanism that powers terrestrial dust devils (tornadoes are formed by a different process entirely). Because the Martian vortices do not form under a cloud base, and are created in a manner simi
    • I can walk into a massive dust devil, spin around like the tazmanian devil in looney tunes, act like it's my spinning that's causing the thing to spin. I'll come out generally unharmed. (Maybe a bit irritated from bits of dust hitting my skin, or maybe a bit of dirt in my eyes and/or nostrils -- but otherwise quite unharmed.)

      OTOH, I tend to avoid (and flee from) tornadoes, as there's a high degree of certainty if we were to interesect one another, I wouldn't survive.
  • by Anonymous Coward on Saturday July 16, 2005 @09:38AM (#13080869)
    The martian atmosphere is much thinner.. so it isnt gonna be as powerful as "terrestrial hurricanes" for sure..
    • More specifically, Mars's atmosphere is about 0.7% of ours (incredibly thin); "tenuous" would be a good term for it. Even though energy of wind is proportional to velocity squared, this means that the winds (assuming that they're equal to atmospheric density) have the energy of a 6 mph breeze on Earth.

      The problem isn't the force, but the dust. The dust is a problem on its own; it almost seems designed to create static charges and then penetrate tiny cracks in everything around.
  • Thanks :) (Score:5, Funny)

    by HG Slashdot (895363) on Saturday July 16, 2005 @09:39AM (#13080876) Homepage
    But after studying the mini-storms more, they realize that the dust and sand particles could cause static electricity discharges, also known as lightning.
    Thanks :) I have always been wondering what "lightning" is.
    • What is this, li-ght-ning you speak of?
    • Thanks :) I have always been wondering what "lightning" is.

      Last I knew, most American's (and this website has an American bias) experience with lightning was in the form of the rain-storm type. Lightning of this variety isn't a result of dust and sand particles causing static electricity discharges. On a planet that (as far as I know) has no rain, the idea of lightning, isn't obvious. Even though I know lightning can occur in sandstorms, I had never put this together with lightning on Mars.

      So while yo
      • We get heat lightning out here in Ohio from time to time, separate from storms.
        I have what may be a dumb question (There are no dumb questions... Just dumb people asking questions...) but if this thing has rubber tires, couldn't they just put a roll bar on the next one with a lightning rod, and shoot the electricity right out the bottom? Or is the equipment to sensitive to be around a discharge? Electricity has always been something a bit over my head, so if someone on here knows, please share.
        That being
        • I'd expect the rovers are particularly delicate and that they'd be seriously fried by even the smallest lightning strike anywhere near by. Every ounce is a precious commodity on a space probe. The odds of getting hit are nearly zero, so the added weight of a lightning-hardened system would be a big negative on a cost/benefit basis.

          -
        • Electricity as powerful as lightning doesn't care about rubber tires, it'll just go right around them. If lightning travels miles through the sky, and through your car it's not just going to stop there because there are some rubber tires. The equipment on the rovers is no doubt designed to be hearty (It's survived more than a year on another planet with much harsher conditions than earth). But a lightning strike is fairly difficult to route away from electronics without causing some collateral damage.

          -Jes
    • I have always been wondering what "lightning" is.

      Many people [sciam.com] are still wondering what "lightning" is.
  • It was in eastern Washington state - many of them were spinning over hot, dry recently tilled farmland.
    My friend and I were on a road trip, and I asked him to pull over.
    I ran into this thing, and it was really weird - the air around it was still, but the dust devil itself was really windy inside!
    It took only a second or two to walk in and out of it, but it was an interesting experience.
    • There is nothing like experiencing natural weather first hand. Back in the late 80s (I was about 19) we got a really fast thunderstorm with torrential rain. For some odd reason, I was compelled to take my t-shirt off and run into the middle of my back yard. I ran up and grabbed a towel to stick in the back entrance to my house and then threw the t-shirt, shoes and socks off and ran into the storm. I had a friend over who watched in shock as I did this. Since it was a really hot day (mid 90s) the rain f
    • I've been in a dust devil too, in the hot, dry parts in the south-east of Yemen, though it passed over me; I didn't walk into it on purpose.

      It should be pointed out to /.ers who've never seen one that earth ones are nothing like as powerful as the Martian variety, and that all you need to do for safety is to wear sunglasses or something over your eyes and a cloth over your mouth and nose so you don't inhale dust/sand.
    • We used to play in them all the time as kids in southern New Mexico. Most were harmless. But the hill behind our apartment would spawn several strong ones a year that would come down and rip the screen doors off our place. I'd have to find them out in the field and nail them back on the door frame.
  • Wind energy? (Score:2, Interesting)

    by Anonymous Coward
    I know it's a long shot, but couldn't this energy be harnessed in say a decade and make future vehicule be able to function 24/24?
    • Probably, but the devil of it transporting something that can survive the trip in space and not be destroyed too quickly by sand and dust.

      Another problem is, are winds regular and strong enough for the thing to be able to be powered as reliably as solar powered vehicles? If it gets stuck somewhere that isn't windy for a week, that's a week of it being down (once it's reserves run out). On the other hand, the sun rises every day.
  • by MadMorf (118601) on Saturday July 16, 2005 @09:52AM (#13080919) Homepage Journal
    The height of a Martian dust devil can reach 10km (6 miles), which means it's more like the size of a terran tornado

    But no where near the destructive force of a tornado, which may be why they're calling them dust devils...

    It's less than 1/3 the windspeed and since the atmosphere is less dense the total energy will not be anywhere close...
  • Well then (Score:1, Funny)

    by MrShaggy (683273)
    I guess there is no Tasmanian Devil inside these ?? Or a 'really really big one'. Shagz
  • How did Royal Appliance Mfg. Co. [royalappliance.com] manage to build a remote control vacuum cleaner within a vacuum? I am confused! Hopefully this isn't just a trade secret, I hope ot find my answer on uspto.com! ;-)
  • by Cyclotron_Boy (708254) on Saturday July 16, 2005 @10:11AM (#13080983) Homepage
    They bring up an interesting problem in the article about the difficulty of cleaning surfaces after a storm- the triboelectric charges wouldn't necessarily have anywhere to bleed off to. Since Earth's ground is relatively wet, simply sticking a copper rod into the ground provides a good path for stray charges to go. Unfortunately, in a dry soil like that of Mars, grounding rods may not provide the level of protection they might on Earth. On the other hand, the reduced atmospheric pressure and lowered breakdown potential might actually help simpler methods like the charge dissipators (so called "static wicks" [physlink.com]) on plane wings. Basically, as long as there is a sharp point to help field emission and concentrate the E field in a small volume of space, the excess charge is dissipated into the atmosphere.

    • The page you link to, titled "How is a plane protected from Lightning strikes?" references a page "Wingtips [b737.org.uk] by The 737 Technical Site", which says about the static wicks: Note that they are not for lightning protection.

      So, I am a little confused here. They obviously stop some smaller charge build-ups, but what about the lightning issue? Yes or no, and if no, what does protect an airplain from lightning, other then not flying into a storm?
    • The plane is usually constructed with a skin of aluminum that conducts quite nicely, so the lightning heads on out the other side of the plane. The static wicks are more for avoiding problems with radio communications and navigation equipment.
  • "Sand" (Score:4, Informative)

    by luna69 (529007) * on Saturday July 16, 2005 @10:15AM (#13080996)
    The OP notes the "he high speed grains of sand blowing around at about 30 meters/second".

    Just to be clear, we're not talking about "sand" in the sense that your average beachgoer thinks of it. The typical size of the dust grains on Mars is a few tens of microns (say 10-30m or so), which is quite a bit smaller than sand, which ranges from a few hundredths of a millimeter to a couple millimeters in size (roughly, using geological definitions).
    • Very true. What they are calling "sand" is actually more on the order of silt or clay in sedimentary geologic terms. There's a picture of a handy little pocket grain size chart here [isu.edu] for reference.
    • Re:"Sand" (Score:1, Informative)

      by Anonymous Coward
      WTF are you talking!?

      The typical size of the dust grains on Mars is a few tens of microns

      ten microns = 10um

      than sand, which ranges from a few hundredths of a millimeter

      hundreths of a millimeter = 10um

      So you are saying that they have the same size, aren't you?

      (Gratulations to the mods who modded this up. You failed it.)
  • Somebody call the UAC!
  • I was curious to see if the linked article referred to "terran tornados". Nope.

    There's a reference to "terrestrial dustdevils", that's close.

    I would have been surprised to see sci-fi jargon in the middle of a NASA report.
    • I saw and checked the same thing.

      It really irrirates me when SF people (who often should know better). Terra is nothing more then the Latin word for "earth" or "land". It has no more implict value or distiction or anything else over modern-English "Earth". Since all space-traveling cultures speak English anyway (just watch any TV show or movie), "Earth" would be a lot more appropriate then "Terra" ever would.

      As you note, the correct term for "occuring on Earth" is "terrestrial" (which does derive from
  • Apparently Dorthy got her ass to Mars.
  • a potential cause for the loss of ESA's Beagle2? Maybe it's blown off course during landing, or maybe a chance that a Dust Devil went past the lander right after landing and blew it apart? Then maybe it was torn apart and buried under the sand? It would explain why the lander still couldn't be found, 'cause maybe it's not in one piece anymore. Considering this discovery, maybe it would be prudent to figure in a method to avoid lander losses should it encounter any Dust Devils DURING the landig process, in
  • "static electricity discharges, also known as lightning"
    REALLY? Lightning is electricity? Amazing! All along we thought it was from the Gods being angry! Maybe someone should take a kite, and put a key on the string, and fly it in a thunderstorm...
  • This should have been in the natural disasters poll :)
  • Windspeeds of 70mph are not really excessive on Mars.

    The Mariner probes detected a typical wind speed of 125mph and gusts of 300-375mph. (source) [uiuc.edu]

    The reason that these winds are never mentioned is that the atmosphere is so thin (0.75% of the density of Earth's) so they don't have that much force behind them.

  • 70mph is almost enough to push a mobile home off its foundation [noaa.gov]. I imagine it'll push a rover out of the way, or a dough-boy-looking human.
  • At last, we have a fairly reliable way to zero in and find life on Mars. Just find where these funnel-clouds congregate, and you are sure to find Martian trailer parks. Granted, I'm not sure that discovering "green trash" is the type of close encounter everyone's been expecting, but it is better than nothing.
  • by Anonymous Coward
    since they can damage astronauts or equipment on the Martian surface.

    As far as I know, there are no astronauts on Mars so it is not possible for them to be damaged. However, they could be damaged if they were there. Is some kind of backwards Capricorn 1? We actually go there, but don't tell anyone? Conspiracy theorists awake!

  • >>The height of a Martian dust devil can reach 10km (6 miles)

    So, that leaves out even the last option of sending tall astronauts to Mars. :-(
  • The high speed grains of sand blowing around at about 30 meters/second (70 miles per hour) are nothing to blink at either, since they can damage astronauts or equipment on the Martian surface.

    Damage astronauts eh? That doesn't sound good. If it wears and tears on the EVA suits that's bad but if it damages the astronauts that's real bad. I think the state of an astronaut on Mars subject to such elemental damage probably changes in quanta (alive vs. not alive).

  • >"since they can damage astronauts or equipment on the Martian surface".

    Just make sure the astronauts don't take off their space suits.
  • blink (Score:3, Funny)

    by tverbeek (457094) on Saturday July 16, 2005 @02:24PM (#13082283) Homepage
    The high speed grains of sand blowing around at about 30 meters/second (70 miles per hour) are nothing to blink at either,

    I dunno... they sound like a good reason to blink, if you ask me.

  • by FleaPlus (6935) on Saturday July 16, 2005 @03:13PM (#13082607) Journal
    A couple of months ago NASA posted some even better videos of the Martian dust devils, available here:

    http://photojournal.jpl.nasa.gov/catalog/PIA07139 [nasa.gov]
    http://photojournal.jpl.nasa.gov/catalog/PIA07140 [nasa.gov]
    http://photojournal.jpl.nasa.gov/catalog/PIA07138 [nasa.gov]

    There's also a rather neat video of Opportunity escaping from the sand trap [nasa.gov].

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