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

摘要

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