An Infrared Spectral Match Between GEMS and Interstellar Grains

Bradley, J. P.; Keller, L. P.; Snow, Theodore P.; Hanner, M. S.; Flynn, G. J.; Gezo, J. C.; Clemett, S. J.; Brownlee, D. E.; Bowey, J. E.

doi:10.1126/science.285.5434.1716

Cited by 216 publications

(146 citation statements)

References 40 publications

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“…This raises the question: is the chemical composition of ISM grains that we have derived consistent with that of GEMS? The idea that GEMS are unprocessed interstellar grains is supported by a similarity between the shape of the 10 µm feature of some GEMS and that observed for the interstellar medium (Bradley et al 1999b), although also distinct differences can be identified (Bradley et al 1998). In addition, traces of exposure of GEMS to ionizing radiation consistent with an interstellar origin have been reported (Bradley 1994).…”

Section: The Nature Of Gemsmentioning

confidence: 89%

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The shape and composition of interstellar silicate grains

Min

Waters

Koter

et al. 2006

A&A

197

225

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We investigate the composition and shape distribution of silicate dust grains in the interstellar medium. The effects of the amount of magnesium and iron in the silicate lattice are studied in detail. We fit the spectral shape of the interstellar 10 µm extinction feature as observed towards the galactic center using various particle shapes and dust materials. We use very irregularly shaped coated and non-coated porous Gaussian Random Field particles as well as a statistical approach to model shape effects. For the dust materials we use amorphous and crystalline silicates with various composition as well as silicon carbide (SiC). The results of our analysis of the 10 µm feature are used to compute the shape of the 20 µm silicate feature and to compare this with observations of this feature towards the galactic center. By using realistic particle shapes to fit the interstellar extinction spectrum we are, for the first time, able to derive the magnesium fraction in interstellar silicates. We find that the interstellar silicates are highly magnesium rich (Mg/(Fe + Mg) > 0.9) and that the stoichiometry lies between pyroxene and olivine type silicates (O/Si ≈ 3.5). This composition is not consistent with that of the glassy material found in GEMS in interplanetary dust particles indicating that the amorphous silicates found in the Solar system are, in general, not unprocessed remnants from the interstellar medium. Also, we find that a significant fraction of silicon carbide (∼3%) is present in the interstellar dust grains. We discuss the implications of our results for the formation and evolutionary history of cometary and circumstellar dust. We argue that the fact that crystalline silicates in cometary and circumstellar grains are almost purely magnesium silicates is a natural consequence of our findings that the amorphous silicates from which they were formed were already magnesium rich.

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Section: The Nature Of Gemsmentioning

confidence: 89%

“…It has been suggested that GEMS (Glass with Embedded Metal and Sulphides), which are small subgrains found in many IDPs, are unprocessed interstellar dust grains (Bradley et al 1999b). This raises the question: is the chemical composition of ISM grains that we have derived consistent with that of GEMS?…”

Section: The Nature Of Gemsmentioning

confidence: 99%

The shape and composition of interstellar silicate grains

Min

Waters

Koter

et al. 2006

A&A

197

225

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“…The study of anhydrous IDPs has given us a picture of the material from which the solid components of comets are composed : primary silicates (predominantly the orthopyroxene, enstatite, but olivine and clinopyroxenes do occur), organics and glass with embedded metal and sulphides (GEMS). This last component is thought to be original interstellar material (Bradley 1994;Bradley et al 1999). Visible reflectance spectroscopy has been applied to IDPs, in order to compare them with primitive meteorites and with astronomical data (Bradley et al 1996).…”

Section: Meteorites and Interplanetary Dust Particlesmentioning

confidence: 99%

UV-Vis spectroscopy of stardust

Fernandes¹,

Johnson²,

Bridges

et al. 2006

International Journal of Astrobiology

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: NASA's Stardust mission flew through the coma of comet Wild 2 in January 2004, capturing dust grains as it did so. The grains were returned safely to Earth in January 2006, and are in the process of being distributed to investigators. As members of the Spectroscopy Preliminary Examination Team, we are preparing to analyse Stardust grains. Our contribution is to measure the spectrum of the grains between 200 nm (in the near ultraviolet) and 800 nm (near infrared). The purpose of the measurement is to provide an additional technique for characterizing the grains, one that is complementary to other spectroscopic techniques and one that produces results that can be matched directly with spectra acquired remotely (with telescope or spacecraft instrumentation). As part of the preparation for analysis of Stardust materials, we are producing a database of spectra from appropriate minerals, and are honing the technique through analysis of primitive meteorites.

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“…Tiny submicrometer spheroids are likely either solar nebula or presolar interstellar grains [6]. In addition, IDP isotopic anomalies of H, N, O indicate a presolar or interstellar origin.…”

Section: Interplanetary Dustmentioning

confidence: 99%

“…6 An example of impact sensor with PZT's developed for GIADA. The system is open to show the positioning of the piezoelectric sensors below the aluminium sensing plate specific configurations [11][12][13], a minimum momentum of 6.5 × 10 −10 kg m s −1 can be detected.…”

Section: Piezoelectric Sensorsmentioning

confidence: 99%

DuneXpress

et al. 2008

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The DuneXpress observatory will characterize interstellar and interplanetary dust in-situ, in order to provide crucial information not achievable with remote sensing astronomical methods. Galactic interstellar dust constitutes the solid phase of matter from which stars and planetary systems form. Interplanetary dust, from comets and asteroids, represents remnant material from bodies at different stages of early solar system evolution. Thus, studies of interstellar and interplanetary dust with DuneXpress in Earth orbit will provide a comparison between the composition of the interstellar medium and primitive planetary objects. Hence DuneXpress will provide insights into the physical conditions during planetary system formation. This comparison of interstellar and interplanetary dust addresses directly themes of highest priority in astrophysics and solar system science, which are described in ESA's Cosmic Vision. The discoveries of interstellar dust in the outer and inner solar system during the last decade suggest an innovative approach to the characteriza-

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An Infrared Spectral Match Between GEMS and Interstellar Grains

Cited by 216 publications

References 40 publications

The shape and composition of interstellar silicate grains

The shape and composition of interstellar silicate grains

UV-Vis spectroscopy of stardust

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