Physical properties of cometary and interplanetary dust

Levasseur-Regourd, A. C.; Mukai, T.; Lasue, J.; Okada, Yasuhiko

doi:10.1016/j.pss.2006.11.014

Cited by 58 publications

(36 citation statements)

References 47 publications

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“…The elongation of the grains is found by calculating the ratio of the longest and shortest perpendicular axis. Further details are described in the Supplementary Other authors have similarly found good agreement between simulations using aggregates of spheroidal particles and observational data 23,24 . The elongated nature of interstellar dust can be inferred from linear polarisation of starlight due to partially aligned grains 25 .…”

Section: ) It Is Not Yet Clear If This Is An Intrinsic Property Of supporting

confidence: 59%

“…For example Greenberg and Gutasfson 22 suggested that comets aggregate from interstellar grains. They modelled the dust as cylinders with aspect ratios of 2-4 and found good agreement between light scattering experiments and observations.Other authors have similarly found good agreement between simulations using aggregates of spheroidal particles and observational data 23,24 . The elongated nature of interstellar dust can be inferred from linear polarisation of starlight due to partially aligned grains 25 .…”

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confidence: 54%

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Aggregate dust particles at comet 67P/Churyumov–Gerasimenko

Bentley

Schmied

Mannel

et al. 2016

Nature

165

121

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Norway * These authors contributed equally to this workComets are believed to preserve almost pristine dust particles, thus providing a unique sample of the properties of the early solar nebula. The microscopic properties of this dust play a key role in particle aggregation during Solar System formation 1,2 . Prior to Rosetta cometary dust was considered to comprise irregular, fluffy agglomerates based on interpretation of remote observations in the visible and infrared [3][4][5][6] MIDAS, the Micro-Imaging Dust Analysis System 13,14 , is the first spaceborne atomic force microscope (AFM) and a unique instrument designed to measure the size, shape, texture and microstructure of cometary dust. Flying on the Rosetta spacecraft, it collects dust on sticky targets during passive exposures and images its 3D topography with an unprecedented nanometre to micrometre resolution 13 .Cometary dust was first collected in mid-November 2014. In this work we focus on particles collected from then until the end of February 2015. The collected particles cover a range of sizes from tens of micrometres down to a few 100 nanometres, and have various morphologies, from single grains to aggregate particles with different packing densities. Five examples are presented here. Figure 1 shows topographic images (height fields) of three particles (A, B and C). Particles A and C will be referred to as compact, since their sub-units (hereafter grains) are tightly packed, and B appears to be a homogeneous grain. The next example (D) is also a compact particle scanned with a higher lateral resolution of 80 nm (Fig. 2) -a factor four better than the previous scan. The final particle (E), presented in Fig. 3, is best described as a loosely packed "fluffy" aggregate comprising many grains. Detailed collection times and geometries for all particles can be found in Extended Data Fig. 1-3.Aided by the 3D nature of the data, individual grains can be identified, as shown in Fig. 1b, Fig. 2b and 1.09 −0.25 +0.01 µm in size, again similar to the grains in A-C. However, the higher resolution reveals that this micrometre-sized particle is itself an aggregate of smaller units; seven grains can be resolved, with sizes ranging from 260 −120 +50 nm to 540 −250 +20 nm. The visible part of particle E has a maximum extent of 14 µm in X and 37 µm in the Y direction. Analysis of its component grains (Fig. 3d) shows sizes in the range from 0.58 −0.20 +0.15 to 2.57 −0.51 +004 µm with the grain heights ranging between 0.2 µm and 3 µm with 90% smaller than 1.7 µm. These measurements are the first evidence for a continuation of the aggregate nature of dust particles below the size range observed by COSIMA (10s-100s micrometres) 15 .Particle E also shows a morphology strongly reminiscent of stratospheric chondritic porous (CP) IDPs, long suspected of having a cometary origin. This link is consistent with observations by COSIMA for larger dust particles, which also measured similar compositions for dust at 67P and IDPs 15,16 . One notable difference to IDPs is the extre...

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Section: ) It Is Not Yet Clear If This Is An Intrinsic Property Of supporting

confidence: 59%

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confidence: 54%

Aggregate dust particles at comet 67P/Churyumov–Gerasimenko

Bentley

Schmied

Mannel

et al. 2016

Nature

165

121

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“…Ground-based observations of cometary dust mass distributions have also been made. For example, based on observations of comet Hale-Bopp combined with modelling and simulations, it is predicted that the small particle distribution in the size range 0.1 to 20 μm had a sizedistribution slope of −3 (Levasseur- Regourd et al 2007). The time-resolved Stardust data suggest considerable spatial and temporal variation in the size distribution of freshly liberated dust from a single comet, while the cumulative Wild 2 observations seem to suggest differences from comet to comet.…”

Section: Cumulative Size Distribution and Fluxmentioning

confidence: 99%

Characteristics of cometary dust tracks in Stardust aerogel and laboratory calibrations

Burchell

Fairey

Wozniakiewicz

et al. 2008

Meteorit & Planetary Scien

137

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Abstract-The cometary tray of the NASA Stardust spacecraft's aerogel collector was examined to study the dust captured during the 2004 flyby of comet 81P/Wild 2. An optical scan of the entire collector surface revealed 256 impact features in the aerogel (width >100 μm). Twenty aerogel blocks (out of a total of 132) were removed from the collector tray for a higher resolution optical scan and 186 tracks were observed (track length >50 μm and width >8 μm). The impact features were classified into three types based on their morphology. Laboratory calibrations were conducted that reproduced all three types. This work suggests that the cometary dust consisted of some cohesive, relatively strong particles as well as particles with a more friable or low cohesion matrix containing smaller strong grains. The calibrations also permitted a particle size distribution to be estimated for the cometary dust. We estimate that approximately 1200 particles bigger than 1 μm struck the aerogel. The cumulative size distribution of the captured particles was obtained and compared with observations made by active dust detectors during the encounter. At large sizes (>20 μm) all measures of the dust are compatible, but at micrometer scales and smaller discrepancies exist between the various measurement systems that may reflect structure in the dust flux (streams, clusters etc.) along with some possible instrument effects.

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“…When compared with remote and in-situ observations of comets, these data, as well as numerical light-scattering simulations on dust grains and fractal aggregates [8], suggest that compact grains and fluffy dust aggregates are present in cometary comae. And both are made up of rather transparent silicates and absorbing organic material as illustrated in Figure 2.…”

Section: Learning From Space Experimentsmentioning

confidence: 81%