CAREER: Atmospheric Electricity on Earth and Mars

Naturally occurring lightning in the Earth atmosphere releases tremendous amount of energy in a very short time. Lightnings most commonly occur during thunderstorms as electrostatic charges accumulate in clouds. Lightnings have also been found to occur on Mars, believed to be created by dust storms.

Though not as common as on Earth because of low atmosphere pressure, such lightnings can be a hazard to instruments on Mars with metal objects acting like a lightning rod. The multiplication of robotic explorers at the surface of the planet has increased the chances of such electric discharges, increasing risks for instruments and an ever-more likely human-exploration.

This CAREER research outlines a five-year effort to study the physics and observability of electrical discharges in atmospheric conditions representative of Earth and Mars. The investigators suggest a comprehensive study combining theory and experiments centered on discharges produced in air at pressures ranging from 6 to 1013 mbar, to examine the differences between discharges started from a hot, cylindrical or spherical electrode, and the electrification observed in the tribocharging of regoliths and sand grains.

The principal objective is to further our understanding of the physics of electrical discharge in diverse environments. In particular, this research seeks to resolve the following outstanding issues in planetary electricity: (1) Can geometric factors adequately explain the difference between theoretical and observed lightning initiation thresholds? (2) Can modeling help assess the nature (glow, streamer, leader) of atmospheric breakdown occurring in the form of Transient Luminous Events or putative Martian lightning? (3) Can tribocharging lead to the initiation of such non-conventional discharges?

The research plan aims to:

• produce the formulation of a new, generalized model of electron avalanche initiated from a hot cylindrical or spherical electrode,

• create a 3-D fractal models of extraterrestrial discharges and estimates of their electric charges and dipole moments, • make quantitative measurements of the electrification in a scaled Martian dust event, • disseminate of academic research outside academia through Astronomy on Tap talks, and

• create a summer camp using LEGO Mindstorms to introduce middle-schoolers to programing and space science through an innovative and engaging approach.

The success of this project will directly impact the design of future instruments for the detection of extraterrestrial atmospheric electricity by identifying the most measurable changes due to non-conventional lightning. It will also help to assess the risk of initiating discharges from surface objects in particular in the framework of Martian exploration.

It will strengthen the relationship between academic research and the local community, through the 5-day summer camp, public lectures, and talks at informal venues. Through these tasks, the investigator will reach audiences of all ages and levels and seek to inspire the next generation of scientists and engineers.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.