A Challenge for Martian Lightning: Limits of Collisional Charging at Low Pressure

Collisional charging is one potential initial step in generating lightning. In this work, we study the charging of colliding monodisperse, spherical basalt grains depending on ambient pressure.

We used grains of 1.0 to 1.2 mm in one set and 2.0 to 2.4 mm in another set. We varied the ambient pressure between 0.03 mbar and 80 mbar. This especially includes Martian pressure being 6 mbar on average. At a few mbar the net charge gathering on colliding grains has a minimum. A smooth incline in charging occurs for larger pressures. Toward lower pressure the charge increases steeply. The pressure dependence is in agreement to a model where the maximum charge is limited by a gas discharge occurring between two charged colliding grains shortly after or before a collision.

The capability of building up charge is at a minimum exactly in the range of Martian pressures. The charges on grains are at least a factor 5 smaller than at the highest pressure tested and still smaller compared to ambient pressure on Earth. This implies that on Mars collisional charging and the potential of subsequent generation of lightning or other large scale discharges are strongly reduced compared to Earth. This might result in less frequent and less energetic lightning on Mars.

Gerhard Wurm, Lars Schmidt, Tobias Steinpilz, Lucia Boden, Jens Teiser
(Submitted on 27 May 2019)

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Atmospheric and Oceanic Physics (physics.ao-ph)
Journal reference: Icarus 331 (2019) 103-109
DOI: 10.1016/j.icarus.2019.05.004
Cite as: arXiv:1905.11138 [astro-ph.EP] (or arXiv:1905.11138v1 [astro-ph.EP] for this version)
Submission history
From: Gerhard Wurm
[v1] Mon, 27 May 2019 11:37:47 UTC (2,032 KB)
https://arxiv.org/abs/1905.11138
Astrobiology