Browsing Meteoritics & Planetary Science, Volume 43, Number 1-2 (2008) by Subjects
Now showing items 1-2 of 2
Combined micro-Raman, micro-infrared, and field emission scanning electron microscope analyses of comet 81P/Wild 2 particles collected by StardustWe report combined micro-infrared, micro-Raman, and field emission scanning electron microscope (FESEM) analyses of particles collected by the Stardust spacecraft during its flyby of comet 81P/Wild 2 on 2 January 2004 and successfully returned back to Earth on 15 January 2006. We present mid-infrared (IR) spectra of six of these particles. The CH2/CH3 ratios inferred from the infrared data are greater than those seen in organics in the diffuse interstellar medium, possibly indicating the presence of longer or less branched aliphatic chains. The micro-Raman data offer insights into the state of the order of the carbonaceous component present in the particles. Raman parameters for most of the particles span a similar range to that observed in interplanetary dust particles (IDPs) and the most primitive meteorites. Both the IR and Raman data imply the presence of a very labile carbonaceous component. Hydrated silicates may be present in two particles of Track 35, one of which may also contain carbonates, but further investigations with other techniques need to be performed to confirm these findings. In some cases, the analyses are difficult to interpret because of the presence of compressed aerogel mixed with the grains.
Identification of mineral impactors in hypervelocity impact craters in aluminum by Raman spectroscopy of residuesHere we demonstrate the use of Raman spectroscopy techniques to identify mineral particle fragments after their impact into aluminum foil at ~6 km s^(-1). Samples of six minerals (olivine, rhodonite, enstatite, diopside, wollastonite, and lizardite) were fired into aluminum foil and the resulting impact craters were studied with a HeNe laser connected to a Raman spectrometer. Raman spectra similar to those of the raw mineral grains were obtained from the craters for impacts by olivine, rhodonite, enstatite, wollastonite, and diopside, but no Raman signals were found from lizardite after impact. In general, the impactors do not survive completely intact, but are fragmented into smaller fractions that retain the structure of the original body. Combined with evidence for SEM and FIB studies, this suggests that in most cases the fragments are relatively unaltered during impact. The survival of identifiable projectile fragments after impact at ~6 km s^(-1) is thus established in general, but may not apply to all minerals. Where survival has occurred, the use of Raman spectroscopic techniques for identifying minerals after hypervelocity impacts into a metallic target is also demonstrated.