Simulation of Venus Lightning: Radicals and Electrochemical Processes




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study conducted by a joint-training PhD student who is supported by CSC, my effort is supported by WUSTL-MCSS special fund


A new Venus-ESD-Chamber (VEC) and peripheral systems were designed and built to simulate Venus lightning. It consists of three subsystems for (i) electrostatic discharge (ESD) generation, (ii) environmental pressure, temperature, gas composition control & monitoring, and (iii) in-situ optical and non-optical sensors. We conducted arc discharge experiments in air, in CO2 and in simulated Venus atmosphere (SVA) (CO2-N2, 96.5%±1.5%:3.5%±1.5%) under 10, 350, 700, and 1000 mbar pressures, that correspond to the 50-75 km altitude range in Venus cloud layer. The capability of VEC system is firstly demonstrated by observing the plasma emission lines of N, N+, O, Ha and Ar during ESD in air. Photos of ESD-generated plasma show transition from filamentary discharge (FD) to homogenous discharge with increasing duty cycle. Voltage - current curves indicate that the discharge in VEC has the characteristics of arc discharge. Plasma and Raman spectra plus gas sensing revealed the generation of CO2+, CO, CO+, C, C2, C+, O2, O, O+, OH, and O3 in CO2 discharge, and N2, N2+, N, N+, NO, CN, CO2+, CO, CO+, C, C2, C+, O, O+, OH, and O3 in SVA. More atomic emission lines were observed in CO2 (C, C+, O, and O+) and in SVA (N, C, C+, O, and O+) during FD, which generates high ESD voltage. Results suggest that electron flux and kinetic energy are the determining factors for the type of generated radical species but the gas pressure plays a less important role. Follow-up experiments in VEC on minor Venusian atmospheric components, especially SO2, are on-going. The ESD generated radicals and excited atoms/molecules, with high reactivity in electrochemistry and high kinetic energy gained from collision, will definitely induce further electrochemical reactions with Venus atmospheric molecules and with Venusian surface materials.


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