# How strong is the electric charge capacity of Martian dust storms?

In my answer to What would it feel like to be in a Martian dust storm? I assert that Martian dust storms would be best avoided, and as one of the reasons (besides carrying corrosive chemicals like perchlorate salts, hydrogen peroxide, tiny and sharp dust particles being strongly ablative, decreased visibility and so on) I also mention triboelectric charge that such dust storms could cause on the surface of the suit and potentially lead to catastrophic discharge tearing the fabric of the suit.

But there's another possible concern which I also mention, and that is lightnings on Mars. To me, that we directly detected them in 2009 isn't really surprising, since the Martian regolith is covered with rust, iron oxides which gives it its reddish surface tint that the planet is famous for. This got me thinking however, that if Martian dust storms carry sufficient electric potential that its triboelectricity has been suggested as the leading candidate for generating hydrogen peroxide on Mars that was first detected in 2003, such lightnings cannot be rare and far between, and the overall electric charge capacity of these dust storms must be pretty impressive despite their relatively low kinetic strength.

Which brings me to my question. Assuming asking for maximum strength electric discharge events (read: lightnings) would be rather frivolous if we barely detected any (not too surprising considering reduced visibility), perhaps more fruitful would be asking about their average charge capacity that they carry;

Has any orbiter been measuring Martian dust storms capacitance, or can their strength perhaps be established indirectly by measuring its effect on atmospheric chemistry, e.g. local changes in the amount of atmospheric hydrogen peroxide before, during and after the storm?

There are other possible ways of establishing this, including laboratory tests on simulated Martian regolith in Mars-analog atmospheric pressure environment, or even computed models, so I don't want to limit answers to a handful of options that I mentioned to establish this. Any additional insight is welcome, but please provide references in your answers.

• With all that iron-oxide lying around, surely any lightning would have a safe path to the ground already ... ? – Everyone Sep 15 '14 at 17:00
• @Everyone Not necessarily, the top iron oxide layer is rather thin as evidenced by many rovers roaming its surface, so these dust storms would likely lift that top layer into the air, adding to the storm's triboelectricity while reducing ground conductivity. Also, you don't get visible lightning between two conductive plates unless one carries rather strong charge and the other's conductivity is low (or their distance increases, but that's not a case here). So there is capacitance. ;) – TildalWave Sep 15 '14 at 17:07
• Wouldn't the iron oxide layer rise/sink sort-of continuously as the storm moved... the way heat moves in a convective cycle? – Everyone Sep 15 '14 at 17:30
• @Everyone That's a negative (no pun!). :) There would be some direct contact but due to uneven surface topology the lower layer of the storm would be less dense in dust particles than slightly above it. The layer between them also increases in air pressure with the speed of particles above it, creating a surface air cushion. That's essentially what prevents your hard disk's heads from scratching the disk's surface in your computer (assuming you didn't yet switch to SSD). – TildalWave Sep 15 '14 at 17:35

As a Mars dust devil guy, I can say that the ubiquitous dust is NOT generally considered sharp-edged. Almost all of it is one of several clay minerals. Due to the absence of open water and given that the dust has been recycled continuously over many millennia (eroded, transported, deposited, re-eroded, etc), that dust is uniformly fine (2-4$$\mu$$m), "soft" (= clay, perhaps hydrophilic) and rounded plates (clay is platy). It may indeed have hostile chemical components but the dust itself is fine clay.
The electrical environment of the Martian surface has been explored extensively by Wm (Bill) Farrell at NASA Goddard$$\dagger$$. His work will greatly address your interests$$\ddagger$$. I think I'm correctly summarizing it when I say he felt dust devils would lift both clay dust, and silica sand, smashing them together to generate triboelectric charges (+ on the sand, which stays near the base, and - on the clay carried aloft). When these 2 charged materials are separated vertically in the dust devil column, it produces a dipole field. If those charges reach the breakdown voltage threshold for the martian atmosphere, he postulated that "ball lightening" (St. Elmo's Fire) may form. Further, he felt that a proper UV filter might allow lander cameras to see those faint glows during daytime activity of dust devil columns.
$$\ddagger$$ W. Farrell, NASA Goddard, selected papers