Raman spectroscopy of ion-irradiated interplanetary carbon dust analogues

Interplanetary dust particles (IDPs) and meteorites provide a unique opportunity to study extraterrestrial materials in the laboratory. Different Raman studies have shown that most of IDPs exhibit the characteristic amorphous carbon Raman feature. Different degrees of order have been recognized in the amorphous carbon phase of IDPs, testifying either to different origins or to different processing under different physical conditions (temperature, pressure, etc.). This paper presents a comparison between the amorphous carbon Raman features of IDPs and those of carbon dust analogues obtained in the laboratory by ion irradiation of carbon-containing frozen gases and by arc discharge. We propose a possible mechanism able to induce an 'evolution' of IDPs. In particular, amorphous carbon with different degrees of order could be indicative of different irradiation doses by solar wind particles and fast solar protons suffered by IDPs in the interplanetary medium before collection in the Earth's atmosphere. Copyright (C) 2004 John Wiley Sons, Ltd.