Richard A. Kerr

We currently seek a copyright agreement with Science to display abstracts of their cosmochemistry related publications.

Reference
Kerr RA (in press) Roving Into Martian Waters. Science
[doi:10.1126/science.342.6156.304]

Link to Article

Gainsforth et al. (>>10)^*

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Using synchrotron-based X-ray diffraction measurements, we identified crystalline material in two particles of extraterrestrial origin extracted from the Stardust Interstellar Dust Collector. The first particle, I1047,1,34 (Hylabrook), consisted of a mosaiced olivine grain approximately 1 µm in size with internal strain fields up to 0.3%. The unit cell dimensions were a = 4.85 ± 0.08 Å, b  =  10.34 ± 0.16 Å, c  =  6.08 ± 0.13 Å (2σ). The second particle, I1043,1,30 (Orion), contained an olivine grain ≈ 2 µm in length and >500 nm in width. It was polycrystalline with both mosaiced domains varying over ≈ 20º and additional unoriented domains, and contained internal strain fields < 1%. The unit cell dimensions of the olivine were a = 4.76 ± 0.05 Å, b  =  10.23 ± 0.10 Å, c  =  5.99 ± 0.06 Å (2σ), which limited the olivine to a forsteritic composition  >Fo₆₅ (2σ). Orion also contained abundant spinel nanocrystals of unknown composition, but unit cell dimension a  = 8.06 ± 0.08 Å (2σ). Two additional crystalline phases were present and remained unidentified. An amorphous component appeared to be present in both these particles based on STXM and XRF results reported elsewhere.

Reference
Gainsforth et al. (in press) Stardust Interstellar Preliminary Examination VIII: Identification of crystalline material in two interstellar candidates. Meteoritics & Planetary Science
[doi:10.1111/maps.12148]
Published by arrangement with John Wiley & Sons

(The article is temporarily unavailable on the MAPS website.)

Bechtel et al. (>>10)^*

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Under the auspices of the Stardust Interstellar Preliminary Examination, picokeystones extracted from the Stardust Interstellar Dust Collector were examined with synchrotron Fourier transform infrared (FTIR) microscopy to establish whether they contained extraterrestrial organic material. The picokeystones were found to be contaminated with varying concentrations and speciation of organics in the native aerogel, which hindered the search for organics in the interstellar dust candidates. Furthermore, examination of the picokeystones prior to and post X-ray microprobe analyses yielded evidence of beam damage in the form of organic deposition or modification, particularly with hard X-ray synchrotron X-ray fluorescence. From these results, it is clear that considerable care must be taken to interpret any organics that might be in interstellar dust particles. For the interstellar candidates examined thus far, however, there is no clear evidence of extraterrestrial organics associated with the track and/or terminal particles. However, we detected organic matter associated with the terminal particle in Track 37, likely a secondary impact from the Al-deck of the sample return capsule, demonstrating the ability of synchrotron FTIR to detect organic matter in small particles within picokeystones from the Stardust interstellar dust collector.

Reference
Bechtel et al. (in press) Stardust Interstellar Preliminary Examination III: Infrared spectroscopic analysis of interstellar dust candidates. Meteoritics & Planetary Science
[doi:10.1111/maps.12125]
Published by arrangement with John Wiley & Sons

(The article is temporarily unavailable on the MAPS website.)

Stroud et al. (>>10)^*

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The Stardust Interstellar Preliminary Examination team analyzed thirteen Al foils from the NASA Stardust interstellar collector tray in order to locate candidate interstellar dust (ISD) grain impacts. Scanning electron microscope (SEM) images reveal that the foils possess abundant impact crater and crater-like features. Elemental analyses of the crater features, with Auger electron spectroscopy, SEM-based energy dispersive X-ray (EDX) spectroscopy, and scanning transmission electron microscope-based EDX spectroscopy, demonstrate that the majority are either the result of impacting debris fragments from the spacecraft solar panels, or intrinsic defects in the foil. The elemental analyses also reveal that four craters contain residues of a definite extraterrestrial origin, either as interplanetary dust particles or ISD particles. These four craters are designated level 2 interstellar candidates, based on the crater shapes indicative of hypervelocity impacts and the residue compositions inconsistent with spacecraft debris.

Reference
Stround et al. (in press) Stardust Interstellar Preliminary Examination XI: Identification and elemental analysis of impact craters on Al foils from the Stardust Interstellar Dust Collector. Meteoritics & Planetary Science
[doi:10.1111/maps.12136]
Published by arrangement with John Wiley & Sons

(The article is temporarily unavailable on the MAPS website.)