A comparison of triggering conditions for planetary atmospheric electricity on Earth, Venus, and Mars

The in-situ exploration of planetary environments exposes the instrumentation to potential electrostatics hazards and creates the need for an improved understanding of atmospheric electricity beyond Earth. This need is further reinforced by the increasing probability of crewed missions to Mars. Any dielectric breakdown starts when the ambient electric field exceeds some predefined thresholds, which vary with the type of discharge (e.g., leader, streamer, or glow) and its polarity, as well as the atmospheric composition, charge density, pressure, and temperature. Some of these effects are collectively approximated by scaling laws based on either atmospheric scale height, neutral density, or pressure. While these approximations have proven useful in numerical applications, they inherently limit the investigation of each specific parameter independently. To remove this limitation, we introduce a new model, which couples a Boltzmann solver with standard Global Reference Atmospheric Models (GRAM) and lets us perform systematic calculations of the breakdown at every altitude for realistic, altitude dependent gas mixture. We develop profiles from the ground to the ionosphere for Earth, Venus, and Mars and show that for all three planets, classic approximations based on atmospheric scale heights and neutral gas densities become inaccurate respectively above the tropopause and mesopause. We investigate specifically the role of atomic oxygen and atmospheric water. We conclude that hypothesized Martian discharge is favored by the planet's low atmospheric pressure. On Venus, discharges in the cloud layer require charging comparable to Earth thunderstorms' but remain more likely than volcano lightning. We then apply our results to revisit Paschen curves for parallel plates and isolated spherical and cylindrical electrodes. We estimate a critical radius and minimum breakdown voltage that allows ionization of neutral gas and formation of a glow corona around an electrode in air. Additionally, we explore the influence of the gas in which the discharge develops. This allows us to explore the feasibility of a glow corona on other planetary bodies such as Mars. We calculate the breakdown criterion both numerically and analytically to present simplified formulae per each geometry and gas mixture.