| Abstrakt: |
A new Venus‐ESD‐Chamber (VEC) and peripheral systems were designed and built to simulate Venus lightning. It consists of three subsystems (a) electrostatic discharge (ESD) generation, (b) environmental pressure, temperature, gas composition control & monitoring, and (c) optical and non‐optical sensors. We conducted arc discharge experiments in air, in CO2, and in Venus major gas mixture (CO2‐N2, 96.5% ± 1.5%:3.5% ± 1.5%) under 10, 350, 700, and 1,000 mbar pressures, that correspond to the 50–75 km altitude range in the cloud layer of Venus. Plasma and Raman spectra, plus gas sensors, and GC‐MS were used to identify the ESD products and to semi‐quantify CO and O3 generated by ESD. We have found all species of free radicals that have been found in previous simulation studies using different discharge technologies, including some important species in CO2‐N2 system, nitrogen oxides and CN. In addition, we found three species (O3, N2+, and C2) that have not been previously reported. Our results suggest that electron flux and kinetic energy are the determining factors for the type of generated free radical species and gas pressure plays a less important role. We found that the quantity of CO changes with the type of ESD. The detection of O3 in this study suggests that lightning might be one of the sources of O3 observed in the Venusian atmosphere. OI emission line at 777.4 nm is the most prominent line in our plasma spectra of FD, consistent with the intense optical flash observed by the Lightning and Airglow Camera (LAC) on the Akatsuki mission. Plain Language Summary: Lightning is a common phenomenon on Earth and plays an important role in atmospheric chemistry as well as in atmosphere‐surface interaction. The thick atmosphere and strong convective activities in Venus cloud layers could ignite lightning. Evidence of lightning on Venus (optical and electric types) has been reported since the 1970s, including the observation made by the most recent mission Akatsuki in 2020. Here, we report the detection of 15 types of free radicals generated during a set of arc‐type electric discharges in simulated Venus atmosphere with two major Venus gases (CO2 & N2) and in a pressure range corresponding to the Venus cloud layer (50–75 km altitude range). These free radicals are ions and neutral atoms/molecules in excited states, which have extremely high chemical reactivity and high kinetic energy. They could play crucial roles in Venus atmospheric chemistry and might be helpful to interpret some past mission observations for example, nitrogen oxides and O3. Key Points: Building a Venus‐ESD chamber enables simulation of Venus lightning and radical sensingArc discharge was realized to simulate lightning in the cloud layer of Venus15 types of free radicals and excited atoms/molecules were characterized using four sensors [ABSTRACT FROM AUTHOR] |
Plný text