View Full Version : JPL/Mars question
01-19-2009, 03:22 AM
I was just watching a speech (http://www.ted.com/index.php/talks/charles_elachi_on_the_mars_rovers.html) from JPL director Charles Elachi . And he was explaining why the rover lasted so much longer then anyone expected. Turns out that "dust devils" would run over the machine periodically cleaning the dust off the solar panels solving the problem which lead JPL to originally predict it's famous 90 estimation. My question is, with such a low atmospheric pressure on mars, how can a dust devil be obtained? I'm just guess on the dynamics of these miniature tornado but is it not that winds in two separate direction give dust particles enough centripetal force for them to begin to rotate? Where do these winds originate and how, if they exists, can they be strong enough to maintain a vortex.
Note to Mods: I couldn't find an appropriate section to put this question, it seemed Off-topic was only for social things and every other technical section was FIRST based.
01-19-2009, 08:19 AM
Woody there is several threads on rovers that you can find by using the search function at the top of the page. You may find one that was active in the fall when a serious storm threatened the rover. I put forth a solution that parking the rover against a wall in the crater it was near would protect it in the high winds and debris laden storm. I think Dave Lavery answered that they hoped that the winds would keep the panels clear so that when the storm blew itself out, the rover could recharge. Keeping it out of the wind would have comprimised the dust build up. The storm lasted almost a month as I remember and their plan worked. Rover is still going.
01-19-2009, 08:47 AM
I'm no dust devil expert, but they are interesting. Mars is about as close as I want to be from them, or at least tornados. It was after I moved to eastern Massachusetts that I found out this area tends to have the occasional tornado. :( I think there was one that finally touched down east of where I was driving -- the clouds were angry!
Here is what NASA says about them, with explainations: http://science.nasa.gov/headlines/y2005/14jul_dustdevils.htm, which also has a better movie than the one at my favorite Picture of the Day website here http://apod.nasa.gov/apod/ap050426.html
I'm guessing -- I just skimmed the NASA explaination above -- that with the vast plains of Mars that there would be stong winds even with a low atmosphere, and the temperature differential would be enough to get the wind going.
I wonder how easy it would be to build a "homemade" dust devil. I seem to recall seeing one at a science museum. If all it takes is heat (a lamp) and wind (a fan) in some sort of vertical tube, how difficult can it be? Science Fair project, anyone?
Also, Chief Delphi > Other > Math and Science > NASA Discussion is probably the forum to look for.
And on preview, I do remember the discussion Al mentions. I wonder how heavy a rover has to be so it wouldn't get blown over on Mars?
01-19-2009, 08:52 AM
No matter what pressure you are at atmospheric dynamics are basically the same. Hot air moves to cold air. This drives all weather everywhere that we have seen. So even with less pressure there is weather, and wind; all dust devils are is wind moving in a column.
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