09:00 〜 10:30
[PPS04-P05] Semi-quantification of CO and O3 and free radicals detection during simulated Venus electric discharges
キーワード：Venus, lightning , electrochemistry, plasma spectra
Introduction: Lightning is a significant electrical process that can occur on planets with an atmosphere and has been detected on many planets in our solar system. Venusian landers, orbiters, and ground-based telescopes have detected some signals that might come from lightning or some types of electric activities on Venus [1]. An intense optical flash with a few hundred milliseconds duration was observed on March 1, 2020, by Lightning and Airglow Camera (LAC) that covers 552-777 nm on the Akatsuki mission, which was assigned to lightning [2]. More mission observations will have to be made to address the issue of optical detection of Venus lightning.
Lightning would generate free radicals with high chemical activity. Electrochemical reactions among these active species, and with other molecules in Venus atmosphere can create new species. Electrochemistry induced by lightning or electric activities is expected to play an important role in Venus atmospheric chemistry, which is the goal of the current investigation.
Experiments: We conducted electrostatic discharge (ESD) experiments in a newly designed Venus-ESD-Chamber (VEC), within Venus major gas mixture (3.5% N2 + 96.5% CO2) at 10, 350, 700, and 1000 mbar pressures to simulate Venusian lightning in 50-75 km range in the Venus cloud layer. Plasma and Raman spectroscopy, multi-gas sensor, and a GC-MS system were used to identify the ESD produced free radicals and to semi-quantify CO and O3 among them. The details in the experimental setup are reported by ref [3].
Results: Arc type of ESD was generated in VEC in two forms, filamentary discharge (FD) and homogenous discharge (HD). The plasma spectra were collected in situ, shown in Fig. 1. The emission lines of CO2+, CO*, CO+, CI*, C2*, CII, OI*, OII, N2*, N2+, NI*, NII, CN*, and NO* were observed. Fig. 1a was collected during FD where more atomic emission lines were detected (OI*, OII, CI*, CII, NI*, NII, and those from NO*, and CN*). Fig. 1b and 1c were collected during HD where molecular emission lines dominate.
O3 was measured at 1000 mbar because the multi-gas detector was designed to work at atmospheric pressure only. The concentrations of CO in discharge products were quantified using a GC-MS system (at 28 kV and 20 kHz) in Venus major gas mixture, at 100 (100% duty cycle) and 1000 (8% and 100% duty cycle) mbar.
Overall, in this study, 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 the CO2-N2 system, e.g., NO and CN. In addition, we found three species (O3, N2+, and C2) that have not previously been reported. We found the quantity of CO changes with the types of discharges (FD or HD). The detection of O3 in this study suggests that lightning might be one of the sources of O3 observed in the Venusian atmosphere (ref). OI emission line at 777.4 nm is the most prominent line in our plasma spectra, consistent with the intense optical flash observed by Lightning and Airglow Camera (LAC) that covers 552-777 nm on the Akatsuki mission.
Acknowledgments: This experimental investigation was supported by the CSC scholarship (NO. 201906220244) for HKQ to support his joint-training PhD study at Washington University in St. Louis (WUSTL), and by a special funding 94351A from McDonnell Center for Space Sciences (MCSS) at WUSTL to AW to maintain a collaboration with planetary scientists and students from Shandong University in China. The purchase and installation of a new GC-MS system at WUSTL was funded by a new NASA Solar System Working (SSW) project (SSW-80NSSC21K-1832) accompanied by a Planetary Major Equipment and Facility (PMEF) funding with cost sharing from Dept. of Earth and Planetary Science (EPS) and MCSS of WUSTL.
Reference: [1] Lorenz, R. D. (2018) PROG EARTH PLANET SC, 5(1), 1-25, 2018. [2] Takahashi, Y., et al., (2021) Research Square. [3] Qu, H. K., et al., (2023) JGR.
Lightning would generate free radicals with high chemical activity. Electrochemical reactions among these active species, and with other molecules in Venus atmosphere can create new species. Electrochemistry induced by lightning or electric activities is expected to play an important role in Venus atmospheric chemistry, which is the goal of the current investigation.
Experiments: We conducted electrostatic discharge (ESD) experiments in a newly designed Venus-ESD-Chamber (VEC), within Venus major gas mixture (3.5% N2 + 96.5% CO2) at 10, 350, 700, and 1000 mbar pressures to simulate Venusian lightning in 50-75 km range in the Venus cloud layer. Plasma and Raman spectroscopy, multi-gas sensor, and a GC-MS system were used to identify the ESD produced free radicals and to semi-quantify CO and O3 among them. The details in the experimental setup are reported by ref [3].
Results: Arc type of ESD was generated in VEC in two forms, filamentary discharge (FD) and homogenous discharge (HD). The plasma spectra were collected in situ, shown in Fig. 1. The emission lines of CO2+, CO*, CO+, CI*, C2*, CII, OI*, OII, N2*, N2+, NI*, NII, CN*, and NO* were observed. Fig. 1a was collected during FD where more atomic emission lines were detected (OI*, OII, CI*, CII, NI*, NII, and those from NO*, and CN*). Fig. 1b and 1c were collected during HD where molecular emission lines dominate.
O3 was measured at 1000 mbar because the multi-gas detector was designed to work at atmospheric pressure only. The concentrations of CO in discharge products were quantified using a GC-MS system (at 28 kV and 20 kHz) in Venus major gas mixture, at 100 (100% duty cycle) and 1000 (8% and 100% duty cycle) mbar.
Overall, in this study, 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 the CO2-N2 system, e.g., NO and CN. In addition, we found three species (O3, N2+, and C2) that have not previously been reported. We found the quantity of CO changes with the types of discharges (FD or HD). The detection of O3 in this study suggests that lightning might be one of the sources of O3 observed in the Venusian atmosphere (ref). OI emission line at 777.4 nm is the most prominent line in our plasma spectra, consistent with the intense optical flash observed by Lightning and Airglow Camera (LAC) that covers 552-777 nm on the Akatsuki mission.
Acknowledgments: This experimental investigation was supported by the CSC scholarship (NO. 201906220244) for HKQ to support his joint-training PhD study at Washington University in St. Louis (WUSTL), and by a special funding 94351A from McDonnell Center for Space Sciences (MCSS) at WUSTL to AW to maintain a collaboration with planetary scientists and students from Shandong University in China. The purchase and installation of a new GC-MS system at WUSTL was funded by a new NASA Solar System Working (SSW) project (SSW-80NSSC21K-1832) accompanied by a Planetary Major Equipment and Facility (PMEF) funding with cost sharing from Dept. of Earth and Planetary Science (EPS) and MCSS of WUSTL.
Reference: [1] Lorenz, R. D. (2018) PROG EARTH PLANET SC, 5(1), 1-25, 2018. [2] Takahashi, Y., et al., (2021) Research Square. [3] Qu, H. K., et al., (2023) JGR.