Comet dust

Comet dust refers to cosmic dust that originates from a comet. Comet dust can provide clues to comets' origin. When the Earth passes through a comet dust trail, it can produce a meteor shower.

Physical characteristicsEdit

SizeEdit

The majority of dust from comet activity is sub-micrometer[1] to roughly micrometer in size.[2][3] However, this fraction is short-lived, as radiation pressure causes them to blow out of the Solar System[4][5] or spiral inwards.[6][7]

The next size class is large, "fluffy"[4][5] or "cluster-type"[8] aggregates of the above grains. These are typically 20-100 micrometers, a size not arbitrary but observed[9] as the porous aggregates tend to fracture[10] or compact.[8][11][12]

Larger particles are micrometeoroids,[13][14] not dust.[15][16] In the absence of a definition from the IAU,[17][18] groups devised their own definitions of dust: smaller than 100 micrometers,[19] 50,[20] 40,[21] 30,[22] and 20 microns,[23] and <10 μm.[24][25][26][16] Some of these dust/micrometeorite definitions are approximate or ambiguous,[27][28][29] some overlapping or self-conflicting.[30][23][22]

The IAU released a formal statement in 2017. Meteoroids are 30 micrometers to 1 meter, dust is smaller, and the term "micrometeoroid" is discouraged (though not micrometeorite).[31] The IMO noted the new definition,[32] but still displays a prior definition on their site.[33] The Meteoritical Society site retains its prior definition, 0.001 cm.[34] The AMS has posted no rigorous definition.[35][36]

CompositionEdit

Dust is generally chondritic in composition. Its monomers contain mafic silicates, such as olivine and pyroxene.[37] Silicates are rich in high-condensation temperature forsterite and enstatite.[27] As these condense quickly, they tend to form very small particles, not merging droplets.

As with chondritic meteoroids, particles contain Fe(Ni) sulfide[38][39] and GEMS (glass with embedded metal and sulfides)[38]

Various amounts of organics (CHON) are present.[40][41][42] Though organics are cosmically abundant, and were widely predicted to exist in comets, they are spectrally indistinct in most telescopes. Organics were only confirmed via mass spectrometry during the Halley flybys.[43][44] Some organics are in the form of PAHs (Polycyclic Aromatic Hydrocarbons).[45][19][46][47][48]

Very small inclusions of presolar grains (PSGs) may be found.[27][48]

Dust and comet originEdit

 
Microscopic view of comet dust particle

The models for the origin of comets are:[49]

  1. the interstellar model,
  2. the Solar System model,
  3. primordial rubble piles,
  4. aggregation of planetesimals in the dust disk around the UranusNeptune region,
  5. cold shells of material swept out by the protostellar wind.

Bulk properties of the comet dust such as density as well as the chemical composition can distinguish between the models. For example, the isotopic ratios of comet and of interstellar dust are very similar, indicating a common origin.

The 1) interstellar model says that ices formed on dust grains in the dense cloud that preceded the Sun. The mix of ice and dust then aggregated into a comet without appreciable chemical modification. J. Mayo Greenberg first proposed this idea in the 1970s.[50][51]

In the 2) Solar System model, the ices that formed in the interstellar cloud first vaporized as part of the accretion disk of gas and dust around the protosun. The vaporized ices later resolidified and assembled into comets. So the comets in this model would have a different composition than those comets that were made directly from interstellar ice.

The 3) primordial rubble pile model for comet formation says that comets agglomerate in the region where Jupiter was forming.

Stardust's discovery of crystalline silicates in the dust of comet Wild 2 implies that the dust formed above glass temperature (> 1000 K) in the inner disk region around a hot young star, and was radially mixed in the solar nebula from the inner regions a larger distance from the star or the dust particle condensed in the outflow of evolved red giants or supergiants. The composition of the dust of comet Wild 2 is similar to the composition of dust found in the outer regions of the accretion disks around newly-forming stars.[52]

A comet and its dust allow investigation of the Solar System beyond the main planetary orbits. Comets are distinguished by their orbits; long period comets have long elliptical orbits, randomly inclined to the plane of the Solar System, and with periods greater than 200 years. Short period comets are usually inclined less than 30 degrees to the plane of the Solar System, revolve around the Sun in the same counterclockwise direction as the planets orbit, and have periods less than 200 years.

A comet will experience a range of diverse conditions as it traverses its orbit. For long period comets, most of the time it will be so far from the Sun that it will be too cold for evaporation of ices to occur. When it passes through the terrestrial planet region, evaporation will be rapid enough to blow away small grains, but the largest grains may resist entrainment and stay behind on the comet nucleus, beginning the formation of a dust layer. Near the Sun, the heating and evaporation rate will be so great, that no dust can be retained. Therefore, the thickness of dust layers covering the nuclei of a comet can indicate how closely and how often a comet's perihelion travels are to the Sun. If a comet has an accumulation of thick dust layers, it may have frequent perihelion passages that don't approach the Sun too closely.

A thick accumulation of dust layers might be a good description of all of the short period comets, as dust layers with thicknesses on the order of meters are thought to have accumulated on the surfaces of short-period comet nuclei. The accumulation of dust layers over time would change the physical character of the short-period comet. A dust layer both inhibits the heating of the cometary ices by the Sun (the dust is impenetrable by sunlight and a poor conductor of heat), and slows the loss of gases from the nucleus below. A comet nucleus in an orbit typical of short period comets would quickly decrease its evaporation rate to the point that neither a coma or a tail would be detectable and might appear to astronomers as a low-albedo near-Earth asteroid.

Further assemblages and bodiesEdit

Dust particles, aided by ices and organics, form "aggregates" [27][38][53] (less often, "agglomerates"[54]) of 30 to hundreds of micrometers. These are fluffy,[19][55] due to the imperfect packing of cluster-type (large) dust particles, and their subsequent, imperfect packing into aggregates.[56]

The next size category is pebbles, of millimeters to centimeters scale.[57][58][59] Pebbles were inferred at 103P/Hartley 2,[60] and imaged directly at 67P/Churyumov-Gerasimenko.[59][57] Astrophysical use of the word "pebble" differs from its geological meaning.[61] In turn, the next-larger geological term, "cobble," has been skipped by Rosetta scientists.[62]

Even larger bodies are "boulders" (decimeter-scale and above) or "chunks." These are rarely seen in the coma, as gas pressure is often insufficient to lift them to significant altitude or escape velocity.[63][64][65]

The building blocks of comets are the putative cometesimals,[66] analogous to planetesimal. Whether the actual cometesimals/planetesimals were pebble-scale,[67] boulder-scale,[68] or otherwise has been a key topic in Solar System and exoplanet research.[55][69][70][71]

(Mis)Use of the term "dust"Edit

At best, "dust" is a collective noun for the non-gas portion of the coma and tail(s). At worst, the term is an English usage, understood well by astronomers in the field, but not to the general public, teachers, and scientists from other fields.[72] The larger solids are more properly called "debris"[73][74][64] or, for all non-gases, the general "particles"[75][76][44] or "grains."[77][56][22]

Comet 2P/EnckeEdit

Encke is officially a dust-poor, gas-rich comet.[6][78][79] Encke actually emits most of its solid mass as meteoroids or "rocks,"[6] not dust. ISO measured no infrared evidence of a classical cometary dust tail due to small particles.[80]

ReferencesEdit

  1. ^ Mukai, T.; Mukai, S.; Kikouchi, S. (1987). "Variation of Grain Properties and the Dust Outbursts". Symposium on the Diversity and Similarity of Comets, ESA SP-278. European Space Agency. pp. 427–30.
  2. ^ Grun, E.; Massonne; Schwehm, G. (1987). "New Properties of Cometary Dust". Symposium on the Diversity and Similarity of Comets, ESA SP-278. European Space Agency. pp. 305–14.
  3. ^ Fernandez, J. (2005). Comets: Nature, Dynamics, Origins, and their Cosmogonical Relevance. Springer. p. 66.
  4. ^ a b Southworth, R. (11 Nov 1964). "Distribution of the Zodiacal Particles". Annals of the New York Academy of Sciences. 119: 54. doi:10.1111/j.1749-6632.1965.tb47423.x. S2CID 85917931.
  5. ^ a b Fechtig, H. (1982). "Cometary Dust In The Solar System". Comets. Tucson: University of Arizona Press. p. 370.
  6. ^ a b c Whipple, Fred (1986). The Mystery of Comets. Cambridge University Press. p. 143. ISBN 9780521324403.
  7. ^ Dermott, S (2001). "Ch. Orbital evolution of interplanetary dust". In Grün E; Gustafson B; Dermott S; Fechtig H (eds.). Interplanetary Dust. SpringerVerlag. pp. 569–39.
  8. ^ a b Zolensky, M.; Lindstrom, D. (Mar 1991). Mineralogy of 12 large 'chondritic' interplanetary dust particles. 1991 LPSC. pp. 161–69.
  9. ^ Ney, E. (1982). "Optical and Infrared Observations of Bright Comets in the Range 0.5 um to 20 um". Comets. Tucson: University of Arizona Press. p. 323.
  10. ^ Simpson, J.; Rabinowitz, D.; Tuzzolino, A.; Ksanfomality, L. (1986). "Halley's comet dust particle mass spectra, flux distributions and jet structures derived from measurements on the Vega-1 and Vega-2 spacecraft". ESA Proceedings of the 20th ESLAB Symposium on the Exploration of Halley's Comet. Volume 2: Dust and Nucleus. European Space Agency. pp. 11–16.
  11. ^ Leinert, C; Roser, S; Buitrago, J (1983). "How to maintain the spatial distribution of interplanetary dust". Astronomy & Astrophysics. 118 (2): 345–57. Bibcode:1983A&A...118..345L.
  12. ^ Mukai, T; fechtig, H (June 1983). "Packing efficient of fluffy particles". Planetary and SpaceScience. 31 (6): 655–58. doi:10.1016/0032-0633(83)90006-5.
  13. ^ Reach, W.; Sykes, M.; Kelley, M. (2003). "Large Particles From Short-Period Comets". Workshop on Cometary Dust in Astrophysics. Houston: Lunar and Planetary Institute.
  14. ^ Kelley, M.; Reach, W.; Woodward, C. (2009). "A Search for Deep Impact's Large Particle Ejecta". Deep Impact as a World Observatory Event: Synergies in Space, Time, and Wavelength. Berlin Heidelberg: Springer-Verlag. p. 125. ISBN 978-3-540-76959-0.
  15. ^ Beech, M; Steel, D (1995). "On the definition of the term 'meteoroid'". Quart. Journ. Roy. Ast. Soc. 36: 281–84. Bibcode:1995QJRAS..36..281B. Sec. 4 Lower size limit: Meteoroid or dust?
  16. ^ a b Rubin, A; Grossman, J (Mar 2010). "Meteorite and meteoroid: New comprehensive definitions". Meteoritics & Planetary Science. 45 (1): 114–22. Bibcode:2010M&PS...45..114R. doi:10.1111/j.1945-5100.2009.01009.x. "...in practice the term is most often applied to objects smaller than approximately 100 um. These size ranges need to be modified." "By this definition, IDPs are particles smaller than 10um.""
  17. ^ Millman, P (1961). "A Report on Meteor Terminology". Journ. Roy. Ast. Soc. Canada. 55 (6): 265. "particle sizes in general smaller than micrometeorites"
  18. ^ "Resolutions Adopted A. By The General Assembly" (PDF). Retrieved 30 Jun 2020. Sec. "Commission 22 (Meteors and Meteorites/Météores et des Meteorites)"
  19. ^ a b c Greenberg, M; Li, A (1997). "Morphological structural and chemical composition of cometary nuclei and dust". Space Science Reviews. 90: 149–61. doi:10.1023/A:1005298014670. S2CID 189789755. "tenth micron particles" "very fluffy aggregates"
  20. ^ Klöck, W; Staderman, F (1994). Mineralogical and chemical relationships of interplanetary dust particles, micrometeorites, and meteorites in. LPI Technical Report 94-02 Workshop on the analysis of interplanetary dust particles. "50 um"
  21. ^ Levasseur-regourd, A; mukai; lasue; okada (2007). "physical properties of comet and interplanetary dust". Planetary and Space Science. 55 (9): 1010–20. Bibcode:2007P&SS...55.1010L. doi:10.1016/j.pss.2006.11.014. "a radius of 20 um for the upper cut-off"
  22. ^ a b c Grun, E; Krüger, H; Srama, R (2019). "The Dawn of Dust Astronomy". Space Science Reviews. 215 (7): number 46. arXiv:1912.00707. Bibcode:2019SSRv..215...46G. doi:10.1007/s11214-019-0610-1. S2CID 208527737. S.3 Multifaceted Scientific Dust Observations "<~ 30 micrometer"
  23. ^ a b Levasseur-Regourd, A; Mukai, T; Lasue, J; Okada, Y (Jun 2007). "Physical properties of comet and interplanetary dust". Planetary and Space Science. 55 (9): 1010–20. Bibcode:2007P&SS...55.1010L. doi:10.1016/j.pss.2006.11.014. "20 um for the upper cut-off" "50 um for the upper cut-off"
  24. ^ Bradley, J; Sandford, S; Walker, R (1988). "11.1 Interplanetary Dust Particles". Meteorites and the Early Solar System. University of Arizona Press. p. 861. "~ 10 um i diamtr" "~ 10-3 cm in dia"
  25. ^ Love, S; Brownlee, D (Jan 1991). "Heating and thermal transformation of micrometeoroids entering the Earth's atmosphere". Icarus. 89 (1): 26–43. Bibcode:1991Icar...89...26L. doi:10.1016/0019-1035(91)90085-8. "10 um"
  26. ^ Coulson, D; Wickramasinghe, N (21 Aug 2003). "Frictional and radiation heating of micron-sized meteoroids in the Earth's upper atmosphere". Mon. Not. R. Astron. Soc. 343 (4): 1123–30. Bibcode:2003MNRAS.343.1123C. doi:10.1046/j.1365-8711.2003.06478.x. "~10 um"
  27. ^ a b c d Brownlee, D; Tsou, P; Aléon, J; et al. (2006). "81P/Wild 2 Under a Microscope". Science. 314 (5806): 1711–6. doi:10.1126/science.1135840. PMID 17170289. S2CID 141128.
  28. ^ Rehder, D (2010). "5.3.3 Intrplntr Ds Ptcls (Prsl Grs)". Chemistry in Space. Wiley-VCH. ISBN 978-3-527-32689-1. "<100um; typically 0.1-20um"
  29. ^ Folco, L; Cordier, C (2015). "9. Micrometeorites". EMU Notes in Mineralogy. "10 um (Rubin and Grossman, 2010)""in the <100 um size fraction, i.e. across the transition between micrometeorites and IDPs"
  30. ^ Rietmeijer, F (Oct 2002). Mesospheric Metal abundances and Meteoric Dust: Analysis of surviving Meteoroids. 34th COSPAR Scientific Assembly/2nd World Space Congress. "stratospheric interplanetary dust particles (IDPs) (2-100 microns)" "debris from progenitors ~30 to ~1,000 microns"
  31. ^ "Definitions of terms in meteor astronomy" (PDF).
  32. ^ Perlerin, V. "Definitions of terms in meteor astronomy (IAU)". Retrieved 30 Jun 2020.
  33. ^ "Glossary". Retrieved 30 Jun 2020.
  34. ^ Benoit, P. "Dust". Retrieved 30 Jun 2020. "0.001 cm in diameter"
  35. ^ "METEOR FAQS". Retrieved 30 Jun 2020.
  36. ^ "Glossary". Retrieved 30 Jun 2020.
  37. ^ Bradley, J; Brownlee, D; Veblen, D (1983). "Pyroxene whiskers and platelets in interplanetary dust: evidence of vapor phase growth". Nature. 301 (5900): 473. Bibcode:1983Natur.301..473B. doi:10.1038/301473a0. S2CID 4303275.
  38. ^ a b c Zolensky, M; Zega, T; Yano, H; Wirick, S; Westphal, A; Weisberg, M; et al. (15 Dec 2006). "Mineralogy and Petrology of Comet 81P/Wild 2 Nucleus Samples". Science. 314 (5806): 1735–9. Bibcode:2006Sci...314.1735Z. doi:10.1126/science.1135842. PMID 17170295. S2CID 25539280.
  39. ^ Zolensky, M; Thomas, K (Nov 1995). "Iron and iron-nickel sulfides in chondritic interplanetary dust particles". Geochimica et Cosmochimica Acta. 59 (22): 4707. Bibcode:1995GeCoA..59.4707Z. doi:10.1016/0016-7037(95)00329-0.
  40. ^ Kissel, J; Sagdeev, R; Bertaux, J; et al. (1986). "Composition of comet Halley dust particles from Vega observations". Nature. 321: 280. Bibcode:1986Natur.321..280K. doi:10.1038/321280a0. S2CID 122405233.
  41. ^ Kissel, J; Brownlee, D; Büchler, K; et al. (1986). "Composition of comet Halley dust particles from Giotto observations". Nature. 321: 336. Bibcode:1986Natur.321..336K. doi:10.1038/321336a0. S2CID 186245081.
  42. ^ Kissel, J; Kruger, F (1987). "The organic component in dust from comet Halley as measured by the PUMA mass spectrometer on board Vega 1". Nature. 326 (6115): 755–60. Bibcode:1987Natur.326..755K. doi:10.1038/326755a0. S2CID 4358568.
  43. ^ Lawler, M; Brownlee, D (1992). "CHON as a component of dust from comet Halley". Nature. 359 (6398): 810–12. Bibcode:1992Natur.359..810L. doi:10.1038/359810a0. S2CID 4314100.
  44. ^ a b Levasseur-Regourd, A; Agarwal, A; Cottin, H; Engrand, C; Flynn, G; Fulle, M; Gombosi, T; et al. (2018). "Cometary Dust". Space Science Reviews. 214 (3): number 64. Bibcode:2018SSRv..214...64L. doi:10.1007/s11214-018-0496-3. S2CID 189791473.
  45. ^ Clemett, S; Maechling, C; Zare, R; Swan, P; Walker, R (1993). "Identification of complex aromatic molecules in individual interplanetary dust particles". Science. 262 (5134): 721–5. Bibcode:1993Sci...262..721C. doi:10.1126/science.262.5134.721. PMID 17812337. S2CID 24398934.
  46. ^ Lisse, C; et al. (2006). "Spitzer spectral observations of the deep impact ejecta" (PDF). Science. 313 (5787): 635–40. Bibcode:2006Sci...313..635L. doi:10.1126/science.1124694. PMID 16840662. S2CID 3024593.
  47. ^ Sandford, S; et al. (2006). "Organics captured from comet 81P/Wild 2 by the Stardust spacecraft". Science. 314 (5806): 1720–4. Bibcode:2006Sci...314.1720S. doi:10.1126/science.1135841. PMID 17170291. S2CID 2727481.
  48. ^ a b Keller, L; Bajt, S; Baratta, G; Borg, J; Bradley, J; Brownlee, D; et al. (15 Dec 2006). "IR Spectroscopy of Comet 81P/Wild 2 Samples Returned by Stardust". Science. 314 (5806): 1728–31. doi:10.1126/science.1135796. PMID 17170293. S2CID 35413527.
  49. ^ Science News 149, June 1, 1996, pp. 346–347.
  50. ^ Greenberg, J (1977). "From dust to comets". Comets, asteroids, meteorites: Interrelations, evolution and origins, Proceedings of the Thirty-Ninth International Colloquium. University of Toledo. p. 491.
  51. ^ Greenberg, J (1982). "What Are Comets Made Of? a Model Based on Interstellar Dust". Comets. Tucson: University of Arizona Press. p. 131. ISBN 0816507694.
  52. ^ Millan-Gabet, Rafael; Malbet, Fabien; Akeson, Rachel; Leinert, Christoph; Monnier, John; Waters, Rens (2006). "The Circumstellar Environments of Young Stars at AU Scales". Protostars and Planets V: 539. arXiv:astro-ph/0603554. Bibcode:2007prpl.conf..539M.
  53. ^ Lorek, S; Gundlach, B; Lacerda, P; Blum, J (2016). "Comet Formation in Collapsing Pebble Clouds: Wh". Astronomy & Astrophysics. 587: A128. doi:10.1051/0004-6361/201526565. "dust grains form fractal aggregates"
  54. ^ Mannel, T; Bentley, M; Schmied, R; Jeszenszky, H; Levasseur-Regourd, A; Romstedt, J; Torkar, K (10/11/16). "Fractal comet dust- a window into the early Solar System". Mon. Not. R. Astron. Soc. 462 (S1): S304-11. Bibcode:2016MNRAS.462S.304M. doi:10.1093/mnras/stw2898. Check date values in: |date= (help)
  55. ^ a b Weissman, P; Asphaug, E; Lowry, S (2004). "Structure and Density of Comet Nuclei". Comets II. University of Arizona Press. p. 337. Tucson "fluffy aggregate"
  56. ^ a b Wooden, D; Ishii, H; Zolensky, M (May 2017). "Cometary Dust: the Diversity of primitive refractory grains". Phil. Trans. Roy. Ast. Soc. A: Math. Engn. 375 (2097). Bibcode:2017RSPTA.37560260W. doi:10.1098/rsta.2016.0260. PMC 5454228. PMID 28554979. Discussion meeting issue “Cometary science after Rosetta” compiled and edited by Geraint H. Jones, Alan Fitzsimmons, Matthew M. Knight, and Matt G. G. T. Taylor "grains" "particles" "hierarchical aggregates" "'clusters'" "compact porous aggregates""highly porous aggregates"
  57. ^ a b Blum, J; Gundlach, B; Krause, M; Fulle, M; Johansen, A; Agarwal, J; vonBorstel, I; et al. (Jul 2017). "Evidence for the formation of comet 67P/Churyumov-Gerasimenko through gravitational collapse of a bound clump of pebbles". Mon. Not. R. Astron. Soc. 469 (S2): S755-73. arXiv:1710.07846. Bibcode:2017MNRAS.469S.755B. doi:10.1093/mnras/stx2741. S2CID 119230851.
  58. ^ Kretke, K; Levison, H (Dec 2015). "Evidence for Pbs in Cms". Icarus. 262: 9–13. arXiv:1509.00754. doi:10.1016/j.icarus.2015.08.017. S2CID 117797138.
  59. ^ a b Fulle, M; Altobelli, N; Buratti, B; Choukroun, M; Fulchignoni, M; Grün, E; Taylor, M; et al. (Nov 2016). "Unexpected and significant findings in comet 67P/Churyumov-Gerasimenko:an interdisciplinary view". Mon. Not. R. Astron. Soc. 462: S2-8. Bibcode:2016MNRAS.462S...2F. doi:10.1093/mnras/stw1663. "cm-sized pebbles"
  60. ^ Hermalyn, B; Farnham, T; Collins, S; Kelley, M; A'Hearn, M; Bodewits, D; Carcich, B; et al. (2013). "The detection, localization, and dynamics of large icy particles surrounding Comet 103P/Hartley 2". Icarus. 222 (2): 625–33. Bibcode:2013Icar..222..625H. doi:10.1016/j.icarus.2012.09.030. "dust, ice, and hundreds of discrete millimeter to decimeter sized particles."
  61. ^ Dones, L; Brasser, R; Kaib, N; Rickman, H (2015). "Origin and Evolution of the Cometary Reservoirs". Space Science Reviews. 197 (1–4): 191–69. Bibcode:2015SSRv..197..191D. doi:10.1007/s11214-015-0223-2. S2CID 123931232. "so the astrophysical use of the word "pebble" differs from its geological meaning."
  62. ^ Pajola, M; et al. (2016). "The Agilkia boulders/pebbles size–frequency distributions: OSIRIS and ROLIS joint observations of 67P surface". Mon. Not. R. Astron. Soc. 462: S242–52. Bibcode:2016MNRAS.462S.242P. doi:10.1093/mnras/stw2720. "Since inside the Rosetta team the word ‘cobbles’ has never been used, while it has been used ‘pebble’ ... we suggest here to use the word ‘pebble’ for the 0.25 m > size > 0.002 m range. Below 0.002 m the term ‘particle’ is used."
  63. ^ Poulet, F; Lucchetti, A; Bibring, J; Carter, J; Gondet; et al. (2016). "Origin of the local structures at the Philae landing site and implications on the". Mon. Not. R. Astron. Soc. 462: S23. doi:10.1093/mnras/stw1959.
  64. ^ a b Pajola, M; Luccheti, A; Fulle, M; Mottola, S; Hamm, M; Da Deppo, V (17). "The Pebbles/boulders size distribution on Sais: Rosetta's final landing site on Comet 67P/Churyumov-Gerasimenko". Mon. Not. R. Astron. Soc. 469: S636. Bibcode:2017MNRAS.469S.636P. doi:10.1093/mnras/stx1620. Check date values in: |date= (help) " ejected chunks with diameter bigger than few meters""chunks up to the radius of 0.4 m"
  65. ^ Güttler, C; Mannel, T; Rotundi, A; Merouane, S; Fulle, M; Bockelee-Morvan, D; lasue, J; et al. (2019). "Synthesis of the morphological description of cometary dust at comet 67P/Churyumov-Gerasimenko". Astronomy & Astrophysics. 630: A24. arXiv:1902.10634. Bibcode:2019A&A...630A..24G. doi:10.1051/0004-6361/201834751. S2CID 119074609. "small, decimeter-sized boulders"
  66. ^ A'Hearn, M (2006). "Whence Comets?". Science. 314 (5806): 1708–9. Bibcode:2006Sci...314.1708A. doi:10.1126/science.1137083. PMID 17170287. S2CID 43461600.
  67. ^ Lorek, S; Lacerda, P; Blum, J (2018). "Local growth of dust- and ice-mixed aggregates as building blocks in the solar nebula". Astronomy & Astrophysics. 611: A18. doi:10.1051/0004-6361/201630175.
  68. ^ Weissman, P; A'Hearn, M (Nov 2015). "Accretion of Cometary Nuclei in the Solar Nebula: Boulders, Not Pebbles". Aas/Division for Planetary Sciences Meeting Abstracts #47. 309 (5): 309.05. Bibcode:2015DPS....4730905W.
  69. ^ Fulle, M; Blum, J (2017). "Fractal dust constrains the collisional history of comets". Mon. Not. R. Astron. Soc. 469: S39. Bibcode:2017MNRAS.469S..39F. doi:10.1093/mnras/stx971.
  70. ^ Lambrechts, M; Johansen, A (2018). "Forming the cores of giant planets from the radial pebble flux in protoplanetary disks". Astronomy & Astrophysics.
  71. ^ Levasseur-Regourd, A; Baruteau, C; Lasue, J; Milli, J; Renard, J (2020). "Linking studies of tiny meteoroids, zodiacal dust, cometary dust and circumstellar disks". Planetary and Space Science. 186: 104896. arXiv:2003.03116. Bibcode:2020P&SS..18604896L. doi:10.1016/j.pss.2020.104896. S2CID 212628560.
  72. ^ Borovička, J (2016). "About the definition of meteoroid, asteroid, and related terms". WGN, the Journal of the IMO. 44: 31.
  73. ^ Hadjuk, A (1991). "Evolution of Cometary Debris: Physical Aspects". Comets in the Post-Halley Era, Vol. 1. Kluwer. pp. 593–606.
  74. ^ Agarwal, J; A'Hearn, M; Vincent, J; Güttler, C; et al. (Nov 2016). "Acceleration of individual, decimeter-sized aggregates in the lower coma of Comet 67P/Churyumov-Gerasimenko". Mon. Not. R. Astron. Soc. 462 (S1): S78-88. arXiv:1608.07933. Bibcode:2016MNRAS.462S..78A. doi:10.1093/mnras/stw2179. S2CID 52036763.
  75. ^ Stern, S; Jackson, A; Boice, D (1994). "Numerical simulations of particle orbits around 2060 Chiron". Astronomical Journal. 107 (2): 765–71. Bibcode:1994AJ....107..765S. doi:10.1086/116896.
  76. ^ Economou, T; Green, S; Brownlee, D; Clark, B (2013). "DFMI measurements during Stardust-NExT Flyby of Comet 9P/Tempel 1" (PDF). Icarus. 222 (2): 526–39. doi:10.1016/j.icarus.2012.09.019. "clouds of particles resulting from fragmentation of larger aggregates emitted"
  77. ^ Rotundi, A; Sierks, H; Delle Corte, V; Fulle, M; et al. (23 Jan 2015). "Cometary science. Dust measurements in the coma of comet 67P/Churyumov-Gerasimenko inbound to the Sun". Science. 347 (6220): 3905. doi:10.1126/science.aaa3905. PMID 25613898. S2CID 206634190. "grains"
  78. ^ Newburn, R; Spinrad, H (Dec 1985). "Spectrophotometry of seventeen comets. II - The continuum". Astronomical Journal. 90: 2591–2608. Bibcode:1985AJ.....90.2591N. doi:10.1086/113965.
  79. ^ Sekanina, Z (1988). "Outgassing Asymmetry of Periodic Comet Encke I- Apparitions 1924-1984". Astronomical Journal. 95 (3): 911. Bibcode:1988AJ.....95..911S. doi:10.1086/114689. "very low dust content"extremely low dust content"
  80. ^ Reach, W; Sykes, M; Lien, D; Davies, J (2000). "The Formation of Encke Meteoroids and Dust Trail". Icarus. 148 (1): 80. arXiv:astro-ph/0007146. Bibcode:2000Icar..148...80R. doi:10.1006/icar.2000.6478. S2CID 18509697.} "abundant large particles near the comet pose a significant hazard to spacecraft. There is no evidence of a classical cometary dust tail due to small particles."