Tof-sims Analysis of Residues of Projectiles Shot onto Stardust Aluminum

Introduction: The samples from the Stardust space probe will offer the first opportunity for analyzing cometary matter collected under controlled conditions together with contemporary interstellar dust particles [1, 2]. Moreover, Stardust is the first sample return mission ever that provides material from a known solar system object other than the moon. The primary goal after sample arrival is to determine the elemental, isotopic, mineralogical, and organic composition of the dust and thus the properties of the comet’s nucleus. Stardust provides two different types of capture media containing cometary samples [2]. Besides aerogel, about 153 cm of aluminum foils (Al 1100; >99 % pure) were exposed to the comet. These foils were mainly used for fixing and facilitating the removal of the aerogel blocks from the collector trays. Although even small cometary grains are not expected to survive impacts on metal foils unaltered at 6.12 km/s, Al foil might be the primary target material for small (sub-μm) or fluffy particles that disintegrate by penetrating the aerogel and thus cannot be extracted easily from the highly porous and friable capture material. In this ongoing study [3, 4], time-of-flight secondary ion mass spectrometry (TOF-SIMS) was used for the analysis of crater residues on Al foil from impact experiments using material from the Allende meteorite, a hornblende standard, and coal from the Illinois basin. The major goal of this investigation is to evaluate how well the chemical composition of the projectile materials can be reproduced by TOF-SIMS analysis. Samples and Experimental Procedures: Powdered bulk material of the CV3 chondrite Allende, powdered hornblende (Kakanui, USNM 143965), and powdered coal (Illinois) were shot onto Al foil using a 5 mm caliber Light Gas Gun at NASA Johnson Space Center. The following table summarizes grain size ranges and impact velocities of the different projectiles.