Nondestructive 3d Confocal Laser Imaging with Deconvolution of Seven Whole Stardust Tracks with Complementary Xrf and Quantitative Analysis

Introduction: The Stardust mission to comet Wild 2 trapped many cometary and ISM particles in aerogel, leaving behind 'tracks' of melted silica aerogel on both sides of the collector [1]. Collected particles and their tracks range in size from submicron to millimeter scale. Interstellar dust collected on the obverse of the aerogel collector is thought to have an average track length of ~15μm [2,3]. It has been our goal to perform a total non-destructive 3D textural and XRF chemical analysis on both types of tracks. To that end, we use a combination of Laser Confocal Scanning Microscopy (LCSM) and X Ray Florescence (XRF) spectrometry [4]. Utilized properly, the combination of 3D optical data and chemical data provides total nondestructive characterization of full tracks, prior to flattening or other destructive analysis methods. Our LCSM techniques allow imaging at 0.075 μm/pixel, without the use of oil-based lenses. A full textural analysis on track #82 is presented here as well as analysis of 6 additional tracks contained within 3 keystones (#128, #129 and #140). We present a method of removing the axial distortion inherent in LCSM images, by means of a computational 3D Deconvolution algorithm, and present some preliminary experiments with computed point spread functions. The combination of 3D LCSM data and XRF data provides invaluable information, while preserving the integrity of the samples for further analysis. It is imperative that these samples, the first extraterrestrial solids returned since the Apollo era, be fully mapped nondestructively in 3D, to preserve the maximum amount of information prior to other, destructive analysis. Samples and Imaging: Four keystones containing a total of seven tracks were imaged: T82 (898μm carrot), T128a (520μm carrot), T128b (250μm carrot), T128g (40μm carrot), T128d (30μm carrot), T129 (600μm carrot), and T140 (>4100μm bulbous). LCSM images were taken at the American Museum of Natural History Microscopy and Imaging Facility. Scans of varying magnification on regions of tracks #82, #128, #129, and #140 were performed without disturbing the keystone. The Zeiss LSM 510 at the AMNH currently images using dry microscopy at a maximum resolution of ~70nm/voxel edge. Earlier work demonstrated the feasibility of wet microscopy with resolution at or better than 0.04 μm/pixel edge on a stardust analog sample [5]. Table 1 lists for each scan the
 effective magnification (mag), scan speed/pixel dwell time (t, μsec), pixel size resolution (r, μm/pixel edge), and number of slices (n):