The electrochemical process generated by simulation experiments of Venusian lightning
Authors: qu hongkun , Wang Alian , Thimsen Elijah 
Published: July 2021

The electrochemical process generated by simulation experiments of Venusian lightning
Hongkun Qu1,3, Alian Wang1, and and Elijah Thimsen2
1Dept. of Earth and Planetary Sciences and the McDonnell Center for the Space Sciences, 2McKelvey School of Engineering, Washington University in St. Louis, One Brookings Drive, St. Louis, MO, 63130, USA. One Brookings Drive, St. Louis, MO, 63130, USA. 3Shandong Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, School of Space Science and Physics, Institute of Space Sciences, Shandong University, Weihai, Shandong,264209, China. (hongkun.qu@wustl.edu )
&#160;IntroductionLightning (one type of electrostatic discharge), as an important electrical process for planets with atmosphere, which has been detected on many planets in our solar system, e.g., Earth, Jupiter [1], Saturn [2], Uranus [3], and Neptune [3], and might occur on Mars [4], Venus [5], and Tian [6]. The earliest observation of Venus lightning was reported by Ksanfomaliti &#8230; mission name [7]. Afterward, many more ground-based [8] and mission observations on electrical and optical evidence of Venus lightning were reported [9]. The Venus Climate Orbiter (VCO) and Planet-C, observed an intense optical flash that was assigned to lightning in 2020 [10].Electrons with high kinetic energy generated by Venusian lightning would collide with atmospheric gaseous molecules and dissociate, excite these radicals, including atoms and molecules at excited states, have high chemical activity. Electrochemical reactions among these species would create new species that would not be produced in common Venusian chemical reactions.Experimental resultsWe conducted a series of simulation experiments on Venusian lightning in a newly designed Venus-ESD-Chamber (VEC). We report here the radicals detected during ESD in VEC under CO2 and gas mixture of N2, O2, CO2, H2O, Ar. Different types of discharges would generate numbers of radical species which indicate that electrochemical reactions take place during and after discharge.In collected plasma spectra of ESD in gas mixture, the emission lines of N2, N2+, N, N+, NO, OH, O, O+, Ar, and Ha were observed and may be generated by the following reactions:&#160;N2 + e &#8594; N2* + e &#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; (1)N2 + e &#8594; N2+ + e &#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; (2)N2 + e &#8594; N + N + e &#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; (3)N + e &#8594; N+ + e &#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; (4)O2 + e &#8594; O + O + e &#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; (5)O + e &#8594; O+ + 2e&#160;&#160;&#160;&#160;&#160; &#160;&#160;&#160;&#160;&#160;&#160;&#160; (6)N2 + O &#8594; NO + N&#160;&#160; &#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; (7)H2O + e &#8594; OH + H + e &#160;&#160;&#160;&#160;&#160;&#160; (8)Ar + e &#8594; Ar* + e&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; (9)Emission lines of CO2+, CO, CO+, C, C2, C+, O, O+, and OH were observed in spectra of CO2 electrostatic discharge, the possible electrochemical reactions are as follows:CO2 + e &#8594; CO2* + e &#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; (10)CO2 + e &#8594; CO2+ + 2e&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; (11)CO2 + e &#8594; CO + O + e&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; (12)CO2 + e &#8594; C+ + O2 + 2e&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; (13)CO2 + e &#8594; CO+ + O + 2e&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; (14)&#160;These active radicals would play significant rules in the evolutions of the Venusian atmosphere.Further Work: For the next step, we will conduct ESD in SO2 gas and in SO2 + CO2 gas with different concentrates for investigations of sulfur species generated in ESD.&#160;Acknowledgments: This work was supported by the CSC scholarship (NO. 201906220244) for HKQ to support his joint-training Ph.D. study at Washington University in St. Louis, and by spectral funding 94351A of WUSTL_MCSS to AW to maintain a collaboration with planetary scientists and students from Shandong University in China.&#160;Reference:[1]&#160;&#160;&#160;&#160;&#160; D. A. Gurnett, R. R. Shaw, R. R. Anderson, W. S. Kurth, and F. L. Scarf, Geophys. Res. Lett., 1979.[2]&#160;&#160;&#160;&#160;&#160; K. H. Baines et al., Planet. Space Sci., 2009.[3]&#160;&#160;&#160;&#160;&#160; K. Aplin, Springer Science &amp; Business Media, 2013.[4]&#160;&#160;&#160;&#160;&#160; W. M. Farrell and M. D. Desch, J. Geophys. Res. Planets, 2001.[5]&#160;&#160;&#160;&#160;&#160; W. W. L. Taylor, F. L. SCARF, C. T. RUSSELL, and L. H. BRACE, Nature, 1979.[6]&#160;&#160;&#160;&#160;&#160; R. Lorenz, J. Phys. IV, 2002.[7]&#160;&#160;&#160;&#160;&#160; L. V Ksanfomaliti, F. L. Scarf, and W. W. L. Taylor, Venus, 1983.[8]&#160;&#160;&#160;&#160;&#160; S. A. Hansell, W. K. Wells, and D. M. Hunten, Icarus, 1995.[9]&#160;&#160;&#160;&#160;&#160; R. D. Lorenz, Prog. Earth Planet. Sci., 2018.[10]&#160;&#160;&#160; Y. Takahashi et al., Nat. Portf., 2021.&#160;