Micrometerorite collected from the Antarctic snow.

A micrometeorite is a micrometeoroid that has survived entry through the Earth's atmosphere. Usually found on Earth's surface, micrometeorites differ from meteorites in that they are smaller in size, more abundant, and different in composition. The IAU officially defines meteoroids as 30 micrometers to 1 meter; micrometeorites are the small end of the range (~submillimeter).[1] They are a subset of cosmic dust, which also includes the smaller interplanetary dust particles (IDPs).[2]

Micrometeorites enter Earth's atmosphere at high velocities (at least 11 km/s) and undergo heating through atmospheric friction and compression. Micrometeorites individually weigh between 10−9 and 10−4 g and collectively comprise most of the extraterrestrial material that has come to the present-day Earth.[3]

Fred Lawrence Whipple first coined the term "micro-meteorite" to describe dust-sized objects that fall to the Earth.[4] Sometimes meteoroids and micrometeoroids entering the Earth's atmosphere are visible as meteors or "shooting stars", whether or not they reach the ground and survive as meteorites and micrometeorites.


Micrometeorite (MM) textures vary as their original structural and mineral compositions are modified by the degree of heating that they experience entering the atmosphere—a function of their initial speed and angle of entry. They range from unmelted particles that retain their original mineralogy (Fig. 1 a, b), to partially melted particles (Fig. 1 c, d) to round melted cosmic spherules (Fig. 1 e, f, g, h, Fig. 2) some of which have lost a large portion of their mass through vaporization (Fig. 1 i). Classification is based on composition and degree of heating.[5][6]

Figure 1. Cross sections of different micrometeorite classes: a) Fine-grained unmelted; b) Coarse-grained Unmelted; c) Scoriaceous; d) Relict-grain Bearing; e) Porphyritic; f) Barred olivine; g) Cryptocrystalline; h) Glass; i) CAT; j) G-type; k) I-type; and l) Single mineral. Except for G- and I-types all are silicate rich, called stony MMs. Scale bars are 50µm.
Figure 2. Light microscope images of stony cosmic spherules.

The extraterrestrial origins of micrometeorites are determined by microanalyses that show that:

An estimated 40,000 ± 20,000 tonnes per year (t/yr)[3] of cosmic dust enters the upper atmosphere each year of which less than 10% (2700 ± 1400 t/yr) is estimated to reach the surface as particles.[15] Therefore the mass of micrometeorites deposited is roughly 50 times higher than that estimated for meteorites, which represent approximately 50 t/yr,[16] and the huge number of particles entering the atmosphere each year (~1017 > 10 µm) suggests that large MM collections contain particles from all dust-producing objects in the Solar System including asteroids, comets, and fragments from the Moon and Mars. Large MM collections provide information on the size, composition, atmospheric heating effects and types of materials accreting on Earth while detailed studies of individual MMs give insights into their origin, the nature of the carbon, amino acids and pre-solar grains they contain.[17]

Chemical analysis of the microscopic chromite crystals, or chrome-spinels, retrieved from micrometeorites in acid baths has shown that primitive achondrites, which represent less than half a percent of the MM reaching Earth today, were common among MMs accreting more than 466 million years ago.[18]

Collection sites

Click here to see a seven-minute movie of MMs being collected from the bottom of the South Pole drinking water well.

Micrometeorites have been collected from deep-sea sediments, sedimentary rocks and polar sediments. They were previously collected primarily from polar snow and ice because of their low concentrations on the Earth's surface, but in 2016 a method to extract micrometeorites in urban environments[19] was discovered.[20]

Ocean sediments

Melted micrometeorites (cosmic spherules) were first collected from deep-sea sediments during the 1873 to 1876 expedition of HMS Challenger. In 1891, Murray and Renard found "two groups [of micrometeorites]: first, black magnetic spherules, with or without a metallic nucleus; second, brown-coloured spherules resembling chondr(ul)es, with a crystalline structure".[21] In 1883, they suggested that these spherules were extraterrestrial because they were found far from terrestrial particle sources, they did not resemble magnetic spheres produced in furnaces of the time, and their nickel-iron (Fe-Ni) metal cores did not resemble metallic iron found in volcanic rocks. The spherules were most abundant in slowly accumulating sediments, particularly red clays deposited below the carbonate compensation depth, a finding that supported a meteoritic origin.[22] In addition to those spheres with Fe-Ni metal cores, some spherules larger than 300 µm contain a core of elements from the platinum group.[23]

Since the first collection of HMS Challenger, cosmic spherules have been recovered from ocean sediments using cores, box cores, clamshell grabbers, and magnetic sleds.[24] Among these a magnetic sled, called the "Cosmic Muck Rake", retrieved thousands of cosmic spherules from the top 10 cm of red clays on the Pacific Ocean floor.[25]

Terrestrial sediments

Terrestrial sediments also contain micrometeorites. These have been found in samples that:

The oldest MMs are totally altered iron spherules found in 140- to 180-million-year-old hardgrounds.[27]

Urban micrometeorites

In 2016 a new study showed that flat roofs in urban areas are fruitful places to extract micrometeorites.[19] The "urban" cosmic spherules have a shorter terrestrial age and are less altered than the previous findings.[32]

Amateur collectors may find micrometeorites in areas where dust from a large area has been concentrated, such as from a roof downspout.[33][34][35]

Polar depositions

Micrometeorites found in polar sediments are much less weathered than those found in other terrestrial environments, as evidenced by little etching of interstitial glass, and the presence of large numbers of glass spherules and unmelted micrometeorites, particle types that are rare or absent in deep-sea samples.[5] The MMs found in polar regions have been collected from Greenland snow,[36] Greenland cryoconite,[37][38][39] Antarctic blue ice[40] Antarctic aeolian (wind-driven) debris,[41][42][43] ice cores,[44] the bottom of the South Pole water well,[5][15] Antarctic sediment traps[45] and present day Antarctic snow.[14]

Classification and origins of micrometeorites


Modern classification of meteorites and micrometeorites is complex; the 2007 review paper of Krot et al.[46] summarizes modern meteorite taxonomy. Linking individual micrometeorites to meteorite classification groups requires a comparison of their elemental, isotopic and textural characteristics.[47]

Comet versus asteroid origin of micrometeorites

Whereas most meteorites originate from asteroids, the contrasting make-up of micrometeorites suggests that most originate from comets.

Fewer than 1% of MMs are achondritic and are similar to HED meteorites, which are thought to be from the asteroid 4 Vesta.[48][49] Most MMs are compositionally similar to carbonaceous chondrites,[50][51][52] whereas approximately 3% of meteorites are of this type.[53] The dominance of carbonaceous chondrite-like MMs and their low abundance in meteorite collections suggests that most MMs derive from sources different from those of most meteorites. Since most meteorites derive from asteroids, an alternative source for MMs might be comets. The idea that MMs might originate from comets originated in 1950.[4]

Until recently the greater-than-25-km/s entry velocities of micrometeoroids, measured for particles from comet streams, cast doubts against their survival as MMs.[11][54] However, recent dynamical simulations[55] suggest that 85% of cosmic dust could be cometary. Furthermore, analyses of particles returned from the comet, Wild 2, by the Stardust spacecraft show that these particles have compositions that are consistent with many micrometeorites.[56][57] Nonetheless, some parent bodies of micrometeorites appear to be asteroids with chondrule-bearing carbonaceous chondrites.[58]

Extraterrestrial micrometeorites

The influx of micrometeoroids also contributes to the composition of regolith (planetary/lunar soil) on other bodies in the Solar System. Mars has an estimated annual micrometeoroid influx of between 2,700 and 59,000 t/yr. This contributes to about 1 m of micrometeoritic content to the depth of the Martian regolith every billion years. Measurements from the Viking program indicate that the Martian regolith is composed of 60% basaltic rock and 40% rock of meteoritic origin. The lower-density Martian atmosphere allows much larger particles than on Earth to survive the passage through to the surface, largely unaltered until impact. While on Earth particles that survive entry typically have undergone significant transformation, a significant fraction of particles entering the Martian atmosphere throughout the 60 to 1200-μm diameter range probably survive unmelted.[59]

See also


  1. ^ "Definitions of terms in meteor astronomy" (PDF). Retrieved 25 Jul 2020.
  2. ^ Brownlee, D. E.; Bates, B.; Schramm, L. (1997), "The elemental composition of stony cosmic spherules", Meteoritics and Planetary Science, 32 (2): 157–175, Bibcode:1997M&PS...32..157B, doi:10.1111/j.1945-5100.1997.tb01257.x
  3. ^ a b Love, S. G.; Brownlee, D. E. (1993), "A direct measurement of the terrestrial mass accretion rate of cosmic dust", Science, 262 (5133): 550–553, Bibcode:1993Sci...262..550L, doi:10.1126/science.262.5133.550, PMID 17733236, S2CID 35563939
  4. ^ a b Whipple, Fred (1950), "The Theory of Micro-Meteorites", Proceedings of the National Academy of Sciences, 36 (12): 687–695, Bibcode:1950PNAS...36..687W, doi:10.1073/pnas.36.12.687, PMC 1063272, PMID 16578350
  5. ^ a b c Taylor, S.; Lever, J. H.; Harvey, R. P. (2000). "Numbers, Types and Compositions of an Unbiased Collection of Cosmic Spherules". Meteoritics & Planetary Science. 35 (4): 651–666. Bibcode:2000M&PS...35..651T. doi:10.1111/j.1945-5100.2000.tb01450.x. S2CID 55501064.
  6. ^ Genge, M. J.; Engrand, C.; Gounelle, M.; Taylor, S. (2008). "The Classification of Micrometeorites". Meteoritics & Planetary Science. 43 (3): 497–515. Bibcode:2008M&PS...43..497G. doi:10.1111/j.1945-5100.2008.tb00668.x. S2CID 129161696.
  7. ^ Smales, A. A.; Mapper, D.; Wood, A. J. (1958), "Radioactivation analysis of "cosmic" and other magnetic spherules", Geochimica et Cosmochimica Acta, 13 (2–3): 123–126, Bibcode:1958GeCoA..13..123S, doi:10.1016/0016-7037(58)90043-7
  8. ^ a b Marvin, U. B.; Marvin, M. T. (1967), "Black, Magnetic Spherules from Pleistocene and Recent beach sands", Geochimica et Cosmochimica Acta, 31 (10): 1871–1884, Bibcode:1967GeCoA..31.1871E, doi:10.1016/0016-7037(67)90128-7
  9. ^ Blanchard, M. B.; Brownlee, D. E.; Bunch, T. E.; Hodge, P. W.; Kyte, F. T. (1980), "Meteoroid ablation spheres from deep-sea sediments", Earth Planet. Sci. Lett., vol. 46, no. 2, pp. 178–190, Bibcode:1980E&PSL..46..178B, doi:10.1016/0012-821X(80)90004-7
  10. ^ Ganapathy, R.; Brownlee, D. E.; Hodge, T. E.; Hodge, P. W. (1978), "Silicate spherules from deep-sea sediments: Confirmation of extraterrestrial origin", Science, 201 (4361): 1119–1121, Bibcode:1978Sci...201.1119G, doi:10.1126/science.201.4361.1119, PMID 17830315, S2CID 13548443
  11. ^ a b Raisbeck, G. M.; Yiou, F.; Bourles, D.; Maurette, M. (1986), "10Be and 26Al in Greenland cosmic spherules: Evidence for irradiation in space as small objects and a probable cometary origin", Meteoritics, 21: 487–488, Bibcode:1986Metic..21..487R
  12. ^ Nishiizumi, K.; Arnold, J. R.; Brownlee, D. E.; et al. (1995), "10Be and 26Al in individual cosmic spherules from Antarctica", Meteoritics, vol. 30, no. 6, pp. 728–732, doi:10.1111/j.1945-5100.1995.tb01170.x, hdl:2060/19980213244
  13. ^ Yada, T.; Floss, C.; et al. (2008), "Stardust in Antarctic micrometeorites", Meteoritics & Planetary Science, 43 (8): 1287–1298, Bibcode:2008M&PS...43.1287Y, doi:10.1111/j.1945-5100.2008.tb00698.x
  14. ^ a b Duprat, J. E.; Dobrică, C.; Engrand, J.; Aléon, Y.; Marrocchi, Y.; Mostefaoui, S.; Meibom, A.; Leroux, H.; et al. (2010), "Extreme Deuterium excesses in ultracarbonaceous Micrometeorites from Central Antarctic Snow", Science, 328 (5979): 742–745, Bibcode:2010Sci...328..742D, doi:10.1126/science.1184832, PMID 20448182, S2CID 206524676
  15. ^ a b Taylor, S.; Lever, J. H.; Harvey, R. P. (1998), "Accretion rate of cosmic spherules measured at the South Pole", Nature, 392 (6679): 899–903, Bibcode:1998Natur.392..899T, doi:10.1038/31894, PMID 9582069, S2CID 4373519
  16. ^ Zolensky, M.; Bland, M.; Brown, P.; Halliday, I. (2006), "Flux of extraterrestrial materials", in Lauretta, Dante S.; McSween, Harry Y. (eds.), Meteorites and the Early Solar System II, Tucson: University of Arizona Press
  17. ^ Taylor, S.; Schmitz, J.H. (2001), Peucker-Erhenbrink, B.; Schmitz, B. (eds.), "Accretion of Extraterrestrial matter throughout Earth's history—Seeking unbiased collections of modern and ancient micrometeorites", Accretion of Extraterrestrial Matter Throughout Earth's History/ Edited by Bernhard Peucker-Ehrenbrink and Birger Schmitz; New York: Kluwer Academic/Plenum Publishers, New York: Kluwer Academic/Plenum Publishers, pp. 205–219, Bibcode:2001aemt.book.....P, doi:10.1007/978-1-4419-8694-8_12, ISBN 978-1-4613-4668-5
  18. ^ Golembiewski, Kate (23 January 2017). "Today's Rare Meteorites Were Once Common". Field Museum of Natural History.
  19. ^ a b Suttle, M. D.; Ginneken, M. Van; Larsen, J.; Genge, M. J. (2017-02-01). "An urban collection of modern-day large micrometeorites: Evidence for variations in the extraterrestrial dust flux through the Quaternary". Geology. 45 (2): 119–122. Bibcode:2017Geo....45..119G. doi:10.1130/G38352.1. hdl:10044/1/42484. ISSN 0091-7613.
  20. ^ Broad, William J. (10 March 2017). "Flecks of Extraterrestrial Dust, All over the Roof". The New York Times.
  21. ^ Murray, J.; Renard, A. F. (1891), "Report on the scientific results of the voyage of H.M.S. Challenger during the years 1873–76", Deep-Sea Deposits: 327–336
  22. ^ Murray, J.; Renard, A. F. (1883), "On the microscopic characters of volcanic ashes and cosmic dust, and their distribution in deep-sea deposits", Proceedings of the Royal Society, Edinburgh, 12: 474–495
  23. ^ Brownlee, D. E.; Bates, B. A.; Wheelock, M. M. (1984-06-21), "Extraterrestrial platinum group nuggets in deep-sea sediments", Nature, 309 (5970): 693–695, Bibcode:1984Natur.309..693B, doi:10.1038/309693a0, S2CID 4322517
  24. ^ Brunn, A. F.; Langer, E.; Pauly, H. (1955), "Magnetic particles found by raking the deep-sea bottom", Deep-Sea Research, 2 (3): 230–246, Bibcode:1955DSR.....2..230B, doi:10.1016/0146-6313(55)90027-7
  25. ^ Brownlee, D. E.; Pilachowski, L. B.; Hodge, P. W. (1979), "Meteorite mining on the ocean floor (abstract)", Lunar Planet. Sci., X: 157–158
  26. ^ Crozier, W. D. (1960), "Black, magnetic spherules in sediments", Journal of Geophysical Research, 65 (9): 2971–2977, Bibcode:1960JGR....65.2971C, doi:10.1029/JZ065i009p02971
  27. ^ a b Czajkowski, J.; Englert, P.; Bosellini, A.; Ogg, J. G. (1983), "Cobalt enriched hardgrounds - new sources of ancient extraterrestrial materials", Meteoritics, 18: 286–287, Bibcode:1983Metic..18..286C
  28. ^ Jehanno, C.; Boclet, D.; Bonte, Ph.; Castellarin, A.; Rocchia, R. (1988), "Identification of two populations of extraterrestrial particles in a Jurassic hardground of the Southern Alps", Proc. Lun. Planet. Sci. Conf., 18: 623–630, Bibcode:1988LPSC...18..623J
  29. ^ Mutch, T.A. (1966), "Abundance of magnetic spherules in Silurian and Permian salt samples", Earth and Planetary Science Letters, 1 (5): 325–329, Bibcode:1966E&PSL...1..325M, doi:10.1016/0012-821X(66)90016-1
  30. ^ Taylor, S.; Brownlee, D. E. (1991), "Cosmic spherules in the geologic record", Meteoritics, 26 (3): 203–211, Bibcode:1991Metic..26..203T, doi:10.1111/j.1945-5100.1991.tb01040.x
  31. ^ Fredriksson, K.; Gowdy, R. (1963), "Meteoritic debris from the Southern California desert", Geochimica et Cosmochimica Acta, 27 (3): 241–243, Bibcode:1963GeCoA..27..241F, doi:10.1016/0016-7037(63)90025-5
  32. ^ Broad, William J. (2017-03-10). "Flecks of Extraterrestrial Dust, All Over the Roof". The New York Times. ISSN 0362-4331. Retrieved 2019-04-24.
  33. ^ Staff (2016-12-17). "Finding micrometeorites in city gutters". The Economist. ISSN 0013-0613. Retrieved 2019-04-24.
  34. ^ Williams, A.R. (2017-08-01). "The Man Finding Stardust on Earth". Magazine. Archived from the original on August 4, 2017. Retrieved 2019-04-24.
  35. ^ Muhs, Eric. "Micrometeorites". IceCube: University of Wisconsin. Retrieved 2019-04-24.
  36. ^ Langway, C. C. (1963), "Sampling for extra-terrestrial dust on the Greenland Ice Sheet", Berkeley Symposium, vol. 61, Union Géodésique et Géophysique Internationale, Association Internationale d'Hydrologie Scientifique, pp. 189–197
  37. ^ Wulfing, E. A. (1890), "Beitrag zur Kenntniss des Kryokonit", Neus Jahrb. Für Min., Etc., 7: 152–174
  38. ^ Maurette, M.; Hammer, C.; Reeh, D. E.; Brownlee, D. E.; Thomsen, H. H. (1986), "Placers of cosmic dust in the blue ice lakes of Greenland", Science, 233 (4766): 869–872, Bibcode:1986Sci...233..869M, doi:10.1126/science.233.4766.869, PMID 17752213, S2CID 33000117
  39. ^ Maurette, M.; Jehanno, C.; Robin, E.; Hammer, C. (1987), "Characteristics and mass distribution of extraterrestrial dust from the Greenland ice cap", Nature, 328 (6132): 699–702, Bibcode:1987Natur.328..699M, doi:10.1038/328699a0, S2CID 4254594
  40. ^ Maurette, M.; Olinger, C.; Michel-Levy, M.; Kurat, G.; Pourchet, M.; Brandstatter, F.; Bourot-Denise, M. (1991), "A collection of diverse micrometeorites recovered from 100 tonnes of Antarctic blue ice", Nature, 351 (6321): 44–47, Bibcode:1991Natur.351...44M, doi:10.1038/351044a0, S2CID 4281302
  41. ^ Koeberl, C.; Hagen, E. H. (1989), "Extraterrestrial spherules in glacial sediment from the Transantarctic Mountains, Antarctica: Structure, mineralogy and chemical composition", Geochimica et Cosmochimica Acta, 53 (4): 937–944, Bibcode:1989GeCoA..53..937K, doi:10.1016/0016-7037(89)90039-2
  42. ^ Hagen, E. H.; Koeberl, C.; Faure, G. (1990), Extraterrestrial spherules in glacial sediment, Beardmore Glacier area, Transantarctic Mountain, Antarctic Research Series, vol. 50, pp. 19–24, doi:10.1029/AR050p0019, ISBN 978-0-87590-760-4
  43. ^ Koeberl, C.; Hagen, E. H. (1989), "Extraterrestrial spherules in glacial sediment from the Transantarctic Mountains, Antarctica: Structure, mineralogy and chemical composition", Geochimica et Cosmochimica Acta, 53 (4): 937–944, Bibcode:1989GeCoA..53..937K, doi:10.1016/0016-7037(89)90039-2
  44. ^ Yiou, F.; Raisbeck, G. M. (1987), "Cosmic spherules from an Antarctic ice core", Meteoritics, 22: 539–540, Bibcode:1987Metic..22..539Y
  45. ^ Rochette, P.; Folco, L.; Suavet, M.; Van Ginneken, M.; Gattacceca, J; Perchiazzi, N; Braucher, R; Harvey, RP (2008), "Micrometeorites from the Transantarctic Mountains", PNAS, 105 (47): 18206–18211, Bibcode:2008PNAS..10518206R, doi:10.1073/pnas.0806049105, PMC 2583132, PMID 19011091
  46. ^ Krot, A. N.; Keil, K.; Scott, E. R. D.; Goodrich, C. A.; Weisberg, M. K. (2007), "1.05 Classification of Meteorites", in Holland, Heinrich D.; Turekian, Karl K. (eds.), Treatise on Geochemistry, vol. 1, Elsevier Ltd, pp. 83–128, doi:10.1016/B0-08-043751-6/01062-8, ISBN 978-0-08-043751-4
  47. ^ Genge, M. J.; Engrand, C.; Gounelle, M.; Taylor, S. (2008), "The classification of micrometeorites" (PDF), Meteoritics & Planetary Science, 43 (3): 497–515, Bibcode:2008M&PS...43..497G, doi:10.1111/j.1945-5100.2008.tb00668.x, S2CID 129161696, retrieved 2013-01-13
  48. ^ Taylor, S.; Herzog, G. F.; Delaney, J. S. (2007), "Crumbs from the crust of Vesta: Achondritic cosmic spherules from the South Pole water well", Meteoritics & Planetary Science, 42 (2): 223–233, Bibcode:2007M&PS...42..223T, doi:10.1111/j.1945-5100.2007.tb00229.x
  49. ^ Cordier, C.; Folco, L.; Taylor, S. (2011), "Vestoid cosmic spherules from the South Pole Water Well and Transantarctic Mountains (Antarctica): A major and trace element study", Geochimica et Cosmochimica Acta, 75 (5): 1199–1215, Bibcode:2011GeCoA..75.1199C, doi:10.1016/j.gca.2010.11.024
  50. ^ Kurat, G.; Koeberl, C.; Presper, T.; Brandstätter, Franz; Maurette, Michel (1994), "Petrology and geochemistry of Antarctic micrometeorites", Geochimica et Cosmochimica Acta, 58 (18): 3879–3904, Bibcode:1994GeCoA..58.3879K, doi:10.1016/0016-7037(94)90369-7
  51. ^ Beckerling, W.; Bischoff, A. (1995), "Occurrence and composition of relict minerals in micrometeorites from Greenland and Antarctica—implications for their origins", Planetary and Space Science, 43 (3–4): 435–449, Bibcode:1995P&SS...43..435B, doi:10.1016/0032-0633(94)00175-Q
  52. ^ Greshake, A.; Kloeck, W.; Arndt, P.; Maetz, Mischa; Flynn, George J.; Bajt, Sasa; Bischoff, Addi (1998), "Heating experiments simulating atmospheric entry heating of micrometeorites: Clues to their parent body sources", Meteoritics & Planetary Science, 33 (2): 267–290, Bibcode:1998M&PS...33..267G, doi:10.1111/j.1945-5100.1998.tb01632.x
  53. ^ Sears, D. W. G. (1998), "The Case for Rarity of Chondrules and Calcium-Aluminum-rich Inclusions in the Early Solar System and Some Implications for Astrophysical Models", Astrophysical Journal, 498 (2): 773–778, Bibcode:1998ApJ...498..773S, doi:10.1086/305589
  54. ^ Engrand, C.; Maurette, M. (1998), "Carbonaceous micrometeorites from Antarctica" (PDF), Meteoritics & Planetary Science, 33 (4): 565–580, Bibcode:1998M&PS...33..565E, doi:10.1111/j.1945-5100.1998.tb01665.x, PMID 11543069
  55. ^ Nesvorny, D.; Jenniskens, P.; Levison, H. F.; Bottke, William F.; Vokrouhlický, David; Gounelle, Matthieu (2010), "Cometary origin of the zodiacal cloud and carbonaceous micrometeorites. Implications for hot debris disks", The Astrophysical Journal, 713 (2): 816–836, arXiv:0909.4322, Bibcode:2010ApJ...713..816N, doi:10.1088/0004-637X/713/2/816, S2CID 18865066
  56. ^ Brownlee, D. E.; Tsou, Peter; Aléon, Jérôme; Alexander, Conel M. O.'D.; Araki, Tohru; Bajt, Sasa; Baratta, Giuseppe A.; Bastien, Ron; et al. (2006), "Comet 81P/Wild 2 Under a Microscope" (PDF), Science, 314 (5806): 1711–1716, Bibcode:2006Sci...314.1711B, doi:10.1126/science.1135840, hdl:1885/33730, PMID 17170289, S2CID 141128
  57. ^ Joswiak, D. J.; Brownlee, D. E.; Matrajt, G.; Westphal, Andrew J.; Snead, Christopher J.; Gainsforth, Zack (2012), "Comprehensive examination of large mineral and rock fragments in Stardust tracks: Mineralogy, analogous extraterrestrial materials, and source regions", Meteoritics & Planetary Science, 47 (4): 471–524, Bibcode:2012M&PS...47..471J, doi:10.1111/j.1945-5100.2012.01337.x
  58. ^ Genge, M. J.; Gileski, A.; Grady, M. M. (2005), "Chondrules in Antarctic micrometeorites" (PDF), Meteoritics & Planetary Science, 40 (2): 225–238, Bibcode:2005M&PS...40..225G, doi:10.1111/j.1945-5100.2005.tb00377.x, S2CID 52024153, retrieved 2013-01-13
  59. ^ Flynn, George J.; McKay, David S. (1 January 1990), "An assessment of the meteoritic contribution to the martian soil", Journal of Geophysical Research, 95 (B9): 14497, Bibcode:1990JGR....9514497F, doi:10.1029/JB095iB09p14497

Further reading