An observational upper limit on triboelectric discharge and resulting alteration of atmospheric composition on mars

Mechanical forces between mineral grains or aerosols colliding with one another can create charge separation. When this charge separation builds up to produce a sufficient potential difference, these charges will travel across the distance that separates them, neutralizing the resulting voltage. If this happens within a medium, such as an atmosphere, a flash of light referred to as a triboelectric discharge can be produced. Furthermore, along the path of discharge, electrochemical reactions can be produced altering the gas species along that pathway. If enough discharges occur, the bulk composition of the gas can be altered.

The atmosphere of Mars has long been thought to be an ideal place for this kind of charge separation. The low moisture content of the near surface along with abundant mineral grain dust, saltating sand and the very low molecular breakdown voltages for the martian atmosphere all point towards a significant role for this effect. Moreover, laboratory experiments conducted in 2019 have shown that shaking mineral grains in a mars-like environment within a test tube produces the kinds of discharges that would be expected. Those discharges, under laboratory conditions were further seen to alter the composition of the trapped gasses.

Yet no such discharges have ever been observed on Mars. In our presentation we will describe a highly sensitive survey using the MSL Navigation Cameras which failed to find evidence of triboelectric discharge at night over a sand sheet in Gale Crater. Using this observed non-detection, we are able to set a robust upper limit on triboelectric discharge in the martian atmosphere and the corresponding limit on the amount of chemical change that can be produced in the atmosphere as a result.