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Electrostatics on Mars, Dust devils and electric and magnetic field instruments
Floyd
post Jul 17 2016, 02:25 PM
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I read a Science news story on electric fields in dust storms on Earth LINK. A quick Google leads to NASA research on electric filed on dust devils on earth LINK. Does anyone here know if researches ever considered placing a small instrument to measure electric and magnetic fields on a rover? If Spirit and Opportunity had such instruments, we would have gotten great data during near fatal dust storm and also all the cleaning events they experienced. I would be surprised if a combined magnetic and electric field monitor with data logger could not be built weighing significantly less than an ounce.

Dust devils on earth create huge electric fields of up to 4,000 volts/meter and also contain magnetic fields. It would be good to ground truth this dust lifting phenomenon on Mars.


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Paolo
post Jul 17 2016, 03:43 PM
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I think there is one such instrument on ESA's Schiaparelli due to land next October
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Gerald
post Jul 17 2016, 05:04 PM
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That's a topic of interest since quite some time, in my understanding mainly to find an upper bound of the electrostatic field on Mars, in order to estimate possible hazards for any equipment on Mars. Here a more recent paper.
There is still a puzzle about cause and effect of the Martian dust devils and electrostatics.
As far as I understand, the electrostatic field on Mars is well below breakdown, but any remote measurements from Earth appear to be rather sophisticated.
So, I'm looking forward to Schiaparelli's results, too.
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Floyd
post Jul 17 2016, 08:04 PM
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Great that there will be instruments on Schiaparelli. Doesn't look like Mars 2020 will have this capability and I think all science instruments are selected at this point.


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nprev
post Jul 18 2016, 12:42 AM
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MOD NOTE: Edited topic title for clarity.

EDIT: Twice. biggrin.gif


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katodomo
post Jul 18 2016, 05:53 PM
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For reference: The instrument on Schiaparelli is called MicroARES and is part of the DREAMS instrument package for surface operation.

EPSC Abstract
Flight Model

P.S.: The surface platform of ExoMars 2018, now renamed ExoMars 2020, will also have a Russian-built electric field sensor under the current proposal.

See here (ESA) and here.
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rlorenz
post Jul 23 2016, 01:22 AM
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QUOTE (Floyd @ Jul 17 2016, 10:25 AM) *
I read a Science news story on electric fields in dust storms on Earth LINK. A quick Google leads to NASA research on electric filed on dust devils on earth LINK. Does anyone here know if researches ever considered placing a small instrument to measure electric and magnetic fields on a rover? If Spirit and Opportunity had such instruments, we would have gotten great data during near fatal dust storm and also all the cleaning events they experienced. I would be surprised if a combined magnetic and electric field monitor with data logger could not be built weighing significantly less than an ounce.

The lead author of the paper that triggered this story is Francesca Esposito, the PI of the DREAMS package on Schiaparelli, which includes the MicroARES electric field sensor.
The paper reports E-field measurements on dust in Morocco, allegedly supporting the idea that E-fields enhance dust lifting, although the theory that this would be the case was due to Kok and Renno (whose model results are reproduced in the paper)
I'm not sure the observations in this paper really establish cause vs effect, but certainly dustier circumstances correlate with stronger fields, and it will be interesting to see what the instrument yields at Mars.

QUOTE
Dust devils on earth create huge electric fields of up to 4,000 volts/meter and also contain magnetic fields. It would be good to ground truth this dust lifting phenomenon on Mars.


This is true (though I don't think I've seen any evidence of a static magnetic field, only UHF emissions detected with a coil. As for the E-field, indeed thousands of volts/m are typical in dust devils on Earth, but recall that the breakdown field on Earth is >10,000 V/m. The low surface pressure on Mars is near the minimum of the Paschen curve, and so breakdown may occur at a few hundred V/m, so I'd expect dust devils not to sustain fields much higher than that.
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JRehling
post Aug 12 2016, 12:15 AM
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I'm a non-expert on this, but ultraviolet light plays a role in electrostatics that would be seemingly much different on Mars than Earth. The photoelectric effect can cause discharges at small levels before they build up, which would make me suspect that blowing dust on Mars would be less capable of carrying large charges than on Earth. Now, caveats galore:

That wouldn't apply at night.
Dense dust clouds might block the UV.
That's only one factor and doesn't take into account the different composition of the dust, air, temperature, pressure, humidity.

It's a fascinating topic. As we've seen with the disputed existence of lightning on Venus, this is a kind of area where theory is not very accurately predictive and empirical observations are essential. In fact, certain manifestations of lightning on Earth have been controversial or gone undiscovered into recent times.
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