Is the electron avalanche process in a martian dust devil self-quenching?

• Published in: Icarus (New York, N.Y. 1962) N.Y. 1962), 2015-07, Vol.254, p.333-337
• Main Authors: Farrell, W.M., McLain, J.L., Collier, M.R., Keller, J.W., Jackson, T.J., Delory, G.T.
• Format: Article
• Language: English
• Subjects: Carbon dioxide; Discharge; Electron avalanche; Grains; Low pressure; Lunar And Planetary Science And Exploration; Mars; Mars dust; Mathematical models; Meteorology; Quenching; Space Sciences (General)
• ISSN: 0019-1035; 1090-2643
• DOI: 10.1016/j.icarus.2015.04.003

Viking era laboratory experiments show that mixing tribocharged grains in a low pressure CO2 gas can form a discharge that glows, indicating the presence of an excited electron population that persists over many seconds. Based on these early experiments, it has been predicted that martian dust devils and storms may also contain a plasma and new plasma chemical species as a result of dust grain tribo-charging. However, recent results from modeling suggest a contrasting result: that a sustained electron discharge may not be easily established since the increase in gas conductivity would act to short-out the local E-fields and quickly dissipate the charged grains driving the process. In essence, the system was thought to be self-quenching (i.e., turn itself off). In this work, we attempt to reconcile the difference between observation and model via new laboratory measurements. We conclude that in a Mars-like low pressure CO2 atmosphere and expected E-fields, the electron current remains (for the most part) below the expected driving tribo-electric dust currents (∼10μA/m2), thereby making quenching unlikely.