Identification of organic particles via Raman techniques after capture in hypervelocity impacts on aerogel

Capture of small (micrometre-scale) particles in space occurs at high speeds (typically greater than a few km s(-1)) and impacts at such speeds usually vaporize the projectile. However, impact on a porous, low-density medium such as aerogel is not so disruptive and thus the incident particle may be captured relatively intact, even at speeds of 5-6 km s-1. Analysis and subsequent handling of captured particles require great care, and an in situ technique is required for rapid characterization of the particles. Previously it has been shown that Raman techniques can be used for identifying silicate and oxide mineral grains captured in this fashion. Here it is shown that this is also true for organic materials. Particles of poly(methyl methacrylate) and poly(ethyl methacrylate) were fired into aerogel (density 60 km m(-3)) at speeds of similar to5 km s(-1). The Raman spectra obtained from raw grains are comparable to those obtained in situ from grains captured in aerogel. This shows chemically that these organic particles survive the impact process, and that this technique can be used to identify at least some types of organic materials captured in aerogel at high speeds. Copyright (C) 2004 John Wiley Sons, Ltd.