Ion bombardment of interplanetary dust.

The recent discovery of ion tracks in interplanetary dust and the increasing evidence for carbon and carbunized materials in these objects are strongly suggestive that chemical processing by energetic charged-particle bombardment has occurred during the dust lifetimes. The track density gives a measure of the total ion fluence experienced by the grains. We use this information and laboratory data on the modification of icy surfaces by incident ions and electrons to discuss the likelihood that chondritic interplanetary dust particles could have been processed, by plasma bombardment, from aggregates of particles which had volatile mantles which were eventually eroded. Such a processing would leave carbon and carbunized deposits and can affect estimates of the temperature of formation of these dust grains.