TOF-SIMS analysis of Allende projectiles shot into silica aerogel

Abstract

Powdered Allende projectiles were fired into silica aerogel at 6.1 km/sec in order to evaluate particle retrieval and analysis techniques for samples from the Stardust mission. Since particles may disintegrate and ablate along the penetration paths in a high-porosity aerogel, TOF-SIMS analysis may be a suitable method to determine the distribution of such materials along the tracks as well as potential compositional modifications. Therefore, two 350 micrometer-sized tracks, residing at the surface of a keystone specimen that was flattened between two silicon chips, were analyzed. TOF-SIMS allows for a detailed study of the chemical composition of particles that survived the impact mostly intact and of fine-grained material from disintegrated projectiles. In the investigated keystone, material from light gas gun debris dominated. Besides the two tracks, a continuous, 40-micrometer-thick surface layer of implanted material - probably gun residue - was found. One of the two analyzed tracks is compositionally distinct from this surface layer and is likely to contain residual material of an Allende projectile. The analyses clearly demonstrate that tracks, resulting from impactors in the 5-10 micrometer size range, can be successfully analyzed with TOF-SIMS.