Exposing metal and silicate charges to electrical discharges: Did chondrules form by nebular lightning?

TL;DR

This study tested whether nebular lightning could have formed chondrules by exposing dust samples to electrical discharges, finding limited evidence of melting and suggesting such formation is unlikely.

Contribution

The paper provides experimental evidence challenging the hypothesis that nebular lightning directly formed chondrules in meteorites.

Findings

Minor formation of sintered aggregates

Occasional formation of melt spherules, especially with metallic Ni

Electric discharges unlikely to produce chondrules

Abstract

In order to investigate the hypothesis that dust aggregates were transformed to meteoritic chondrules by nebular lightning, we exposed silicatic and metallic dust samples to electric discharges with energies of 120 to 500 J in air at pressures between 10 and 10^5 Pa. The target charges consisted of powders of micrometer-sized particles and had dimensions of mm. The dust samples generally fragmented leaving the major fraction thermally unprocessed. A minor part formed sintered aggregates of 50 to 500 micrometer. In a few experiments melt spherules having sizes smaller than 180 micrometer in diameter (and, generally, interior voids) were formed; the highest spherule fraction was obtained with metallic Ni. Our experiments indicate that chondrule formation by electric current or by particle bombardment inside a discharge channel is unlikely.