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V-type asteroid

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V-type asteroids, also known as Vestoids, are a class of asteroids whose spectral type is characterized by a strong absorption feature at wavelengths longward of 0.75 μm, similar to that of 4 Vesta, the second-most-massive asteroid in the asteroid belt.[1] These asteroids comprise approximately 6% of main-belt asteroids and are characterized by their basaltic surface composition, making them distinct from other asteroid types.[2]

Characteristics

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Physical Properties

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V-type asteroids are relatively bright objects with moderate to high albedo values typically ranging from 0.20 to 0.40.[3] They are distinguished from other asteroid types by their basaltic composition, which indicates that they originated from differentiated parent bodies that underwent volcanic or igneous processing.[4]

The mean diameter of V-type asteroids varies considerably, from sub-kilometer objects to 4 Vesta itself with a mean diameter of approximately 525 kilometers.[5] Most V-types outside the Vesta family are relatively small, with diameters typically less than 10 kilometers.

Spectral Features

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The electromagnetic spectrum of V-type asteroids exhibits several diagnostic features:[6]

  • A very strong absorption feature longward of 0.75 μm attributed to Fe2+ in pyroxene
  • A second absorption feature centered near 0.9-1.0 μm, also due to pyroxene
  • Very steep red spectral slope shortward of 0.7 μm
  • A weak absorption feature at 0.506 μm due to Fe2+ spin-forbidden transitions in pyroxene

The Band I center position typically ranges from 0.90 to 0.94 μm, while the Band II center is usually located between 1.89 and 2.00 μm.[7] The ratio of Band II to Band I depths (BII/BI) typically ranges from 1.5 to 2.5 for V-type asteroids.

Composition

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V-type asteroids are composed primarily of basaltic material containing pyroxene and plagioclase feldspar.[8] The pyroxene composition is typically low-calcium pyroxene (orthopyroxene) with varying amounts of high-calcium pyroxene (clinopyroxene). The visible and near-infrared spectra of V-type asteroids closely resemble those of basaltic achondrite meteorites, particularly the HED meteorites (Howardites, Eucrites, and Diogenites).[9]

Spectroscopic analysis has revealed compositional variations among V-types:[10]

  • Eucrite-like: High calcium content, consistent with basaltic eucrite meteorites
  • Diogenite-like: Low calcium content, consistent with orthopyroxenitic diogenite meteorites
  • Howardite-like: Intermediate composition, mixture of eucrite and diogenite material

Distribution

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Vesta Family Members

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The vast majority of V-type asteroids are members of the Vesta family along with Vesta itself.[11] The Vesta family is one of the largest asteroid families with more than 15,000 known members.[12] Spectroscopic studies indicate that approximately 85% of the members of the Vesta dynamical family are V-type asteroids.[13]

Mars-Crossing V-types

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Several V-type asteroids have been identified as Mars-crossers, including:[14][failed verification]

Recent systematic searches have confirmed three additional V-type asteroids in the Mars crossing region through spectroscopic observations.[15]

Near-Earth V-types

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Several V-type asteroids have been identified among Near-Earth objects:[16]

Non-Vesta Family V-types

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There is a scattered group of V-type asteroids in the general vicinity of the Vesta family but not dynamically associated with it.[17] As of current surveys, 22 V-type asteroids have been identified outside the Vesta family in the inner asteroid belt:[18]

Middle and Outer Main Belt

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Recent spectroscopic surveys have identified V-type asteroids throughout the main belt:[21]

  • Ten confirmed V-types orbiting in the middle main belt (2.5 < a < 2.82 AU)
  • Five V-types in the outer main belt (a > 2.82 AU)
  • Two V-types identified beyond 3.3 AU

Origin and Formation

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Vesta Origin Hypothesis

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The predominant theory suggests that most V-type asteroids originated as fragments of 4 Vesta's crust during large impact events.[22] NASA's Dawn mission identified two enormous impact basins on Vesta's southern hemisphere:[23]

  • Veneneia basin: ~395 km diameter, formed approximately 2.1 billion years ago
  • Rheasilvia basin: ~505 km diameter, formed approximately 1 billion years ago

These impact events excavated and ejected large amounts of basaltic material from Vesta's crust and upper mantle.[24] The ejected fragments formed the Vesta family and are thought to be the source of the HED meteorites that fall to Earth.

Dynamical Evolution

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V-type asteroids ejected from Vesta have undergone complex dynamical evolution:[25]

  • Fragments initially formed a collisional family near Vesta
  • Yarkovsky effect and YORP effect caused slow orbital drift
  • Interaction with mean-motion and secular resonances dispersed fragments
  • Some fragments entered the 3:1 and ν6 resonances, allowing delivery to Earth-crossing orbits

Multiple Parent Body Hypothesis

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Recent research indicates that V-type asteroids in the middle and outer main belt are unlikely to have originated from Vesta.[26] Extensive numerical simulations demonstrate the lack of efficient dynamical routes to transport Vesta fragments beyond 2.5 AU.[27]

The asteroid 1459 Magnya provides compelling evidence for multiple differentiated parent bodies:[28]

  • Located at 3.14 AU, beyond plausible Vesta ejecta dispersal
  • Spectroscopic differences from Vesta suggest distinct parent body
  • May represent remnant of destroyed differentiated asteroid

Classification Methods

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Photometric Identification

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V-type asteroids can be identified through various observational methods:[29]

  • Visible photometry using SDSS filters (u, g, r, i, z)
  • Near-infrared colors from 2MASS and WISE surveys
  • Combined visible and near-infrared spectroscopy

Spectroscopic Confirmation

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Definitive classification requires spectroscopic observations covering the 0.4-2.5 μm range to identify characteristic pyroxene absorption bands.[30] Key diagnostic parameters include:

  • Band I center position (0.90-0.94 μm)
  • Band II center position (1.89-2.00 μm)
  • Band area ratio (BAR = Band II area/Band I area)
  • Spectral slope

J-type Subclassification

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A J-type classification has been proposed for asteroids exhibiting particularly strong 1 μm absorption bands similar to diogenite meteorites, with Band I centers >0.95 μm.[31] These objects likely sample deeper crustal or upper mantle material from differentiated parent bodies.

Notable Examples

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4 Vesta

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4 Vesta is the archetype of the V-type class and the only intact differentiated asteroid accessible to detailed study.[32] Key characteristics:

  • Mean diameter: 525.4 ± 0.2 km
  • Bulk density: 3.456 ± 0.035 g/cm3
  • Differentiated structure with metallic core (~220 km diameter)
  • Basaltic crust thickness: 12–20 km

1459 Magnya

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1459 Magnya represents the most significant non-Vestoid V-type asteroid:[33]

  • Semi-major axis: 3.14 AU
  • Diameter: ~17 km
  • Spectroscopic properties distinct from Vesta
  • Possible fragment of destroyed differentiated asteroid

2579 Spartacus

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2579 Spartacus shows unusual spectroscopic properties suggesting deep origin:[34]

  • Enhanced olivine content
  • May sample mantle material
  • Located at 2.71 AU

Significance

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Solar System Evolution

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V-type asteroids provide crucial constraints on early Solar System processes:[35]

  • Timeline of planetesimal differentiation (first ~5 Myr)
  • Extent of igneous processing in the asteroid belt
  • Number and distribution of differentiated parent bodies
  • Collisional evolution of the asteroid belt

Meteorite Connections

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V-type asteroids are the likely source of HED meteorites, providing ground-truth for asteroid composition studies.[36] This connection enables:

  • Laboratory analysis of asteroid material
  • Calibration of remote sensing techniques
  • Understanding of space weathering processes
  • Chronology of asteroid belt evolution

Future Research

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Ongoing and future research priorities include:[37]

  • Spectroscopic surveys to identify additional V-types
  • Detailed compositional studies of non-Vestoid V-types
  • Dynamical modeling of V-type distribution
  • Search for olivine-rich V-types sampling mantle material

See also

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References

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  2. ^ Moskovitz, N.A.; et al. (2008). "A spectroscopic comparison of HED meteorites and V-type asteroids in the inner Main Belt". Icarus. 198 (1): 77–90. arXiv:0807.3951. Bibcode:2008Icar..198...77M. doi:10.1016/j.icarus.2008.07.006.
  3. ^ Usui, F.; et al. (2011). "Asteroid Catalog Using Akari: AKARI/IRC Mid-Infrared Asteroid Survey". Publications of the Astronomical Society of Japan. 63 (5): 1117–1138. Bibcode:2011PASJ...63.1117U. doi:10.1093/pasj/63.5.1117.
  4. ^ McCord, T.B.; Adams, J.B.; Johnson, T.V. (1970). "Asteroid Vesta: Spectral Reflectivity and Compositional Implications". Science. 168 (3938): 1445–1447. Bibcode:1970Sci...168.1445M. doi:10.1126/science.168.3938.1445. PMID 17731590.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  5. ^ Russell, C.T.; et al. (2012). "Dawn at Vesta: Testing the Protoplanetary Paradigm". Science. 336 (6082): 684–686. Bibcode:2012Sci...336..684R. doi:10.1126/science.1219381. PMID 22582253.
  6. ^ Pieters, C.M.; et al. (1985). "The Nature of Asteroid 4 Vesta from Mineralogical Studies of the HED Meteorites". Journal of Geophysical Research. 90 (B14): 12393–12413. Bibcode:1985JGR....9012393P. doi:10.1029/JB090iB14p12393.
  7. ^ Gaffey, M.J. (1997). "Surface Lithologic Heterogeneity of Asteroid 4 Vesta". Icarus. 127 (1): 130–157. Bibcode:1997Icar..127..130G. doi:10.1006/icar.1997.5680.
  8. ^ Burbine, T.H.; et al. (2001). "Vesta, Vestoids, and the howardite, eucrite, diogenite group: Relationships and the origin of spectral differences". Meteoritics & Planetary Science. 36 (6): 761–781. Bibcode:2001M&PS...36..761B. doi:10.1111/j.1945-5100.2001.tb01915.x.
  9. ^ McSween, H.Y.; et al. (2011). "HED Meteorites and Their Relationship to the Geology of Vesta and the Dawn Mission". Space Science Reviews. 163 (1–4): 141–174. Bibcode:2011SSRv..163..141M. doi:10.1007/s11214-010-9637-z.
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  13. ^ Moskovitz, N.A.; et al. (2010). "A spectroscopic investigation of the Vesta family". Icarus. 210 (2): 674–684. Bibcode:2010Icar..210..674M. doi:10.1016/j.icarus.2010.07.017.
  14. ^ Ribeiro, A.O.; et al. (2016). "Dynamical study of the Atira group of asteroids". Monthly Notices of the Royal Astronomical Society. 458 (4): 4471–4476. Bibcode:2016MNRAS.458.4471R. doi:10.1093/mnras/stw642.
  15. ^ Roig, F.; Gil-Hutton, R. (2006). "Selecting candidate V-type asteroids from the analysis of the Sloan Digital Sky Survey colors". Icarus. 183 (2): 411–419. Bibcode:2006Icar..183..411R. doi:10.1016/j.icarus.2006.04.002.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  16. ^ Binzel, R.P.; et al. (2004). "Dynamical and compositional assessment of near-Earth object mission targets". Meteoritics & Planetary Science. 39 (3): 351–366. Bibcode:2004M&PS...39..351B. doi:10.1111/j.1945-5100.2004.tb00098.x.
  17. ^ Lazzaro, D.; et al. (2004). "Discovery of a basaltic asteroid in the outer Main Belt". Science. 305 (5690): 1572–1574. Bibcode:2004Sci...305.1572L. doi:10.1126/science.1100416 (inactive 11 September 2025).{{cite journal}}: CS1 maint: DOI inactive as of September 2025 (link)
  18. ^ Hardersen, P.S.; et al. (2014). "More chips off of asteroid (4) Vesta: Characterization of eight Vestoid and V-type asteroids with near-infrared spectroscopy". Icarus. 242: 269–282. arXiv:1408.2731. Bibcode:2014Icar..242..269H. doi:10.1016/j.icarus.2014.08.020.
  19. ^ Hardersen, P.S.; Gaffey, M.J.; Abell, P.A. (2004). "Mineralogy of Asteroid 1459 Magnya and implications for its origin". Icarus. 167 (1): 170–177. Bibcode:2004Icar..167..170H. doi:10.1016/j.icarus.2003.09.022.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  20. ^ Sunshine, J.M.; et al. (2004). "High-calcium pyroxene as an indicator of igneous differentiation in asteroids and meteorites". Meteoritics & Planetary Science. 39 (8): 1343–1357. Bibcode:2004M&PS...39.1343S. doi:10.1111/j.1945-5100.2004.tb00950.x.
  21. ^ Migliorini, A.; et al. (2021). "Characterization of V-type asteroids orbiting in the middle and outer main belt". Monthly Notices of the Royal Astronomical Society. 504 (2): 2019–2032. Bibcode:2021MNRAS.504.2019M. doi:10.1093/mnras/stab332.
  22. ^ Asphaug, E. (1997). "Impact origin of the Vesta family". Meteoritics & Planetary Science. 32 (6): 965–980. Bibcode:1997M&PS...32..965A. doi:10.1111/j.1945-5100.1997.tb01584.x.
  23. ^ Schenk, P.; et al. (2012). "The Geologically Recent Giant Impact Basins at Vesta's South Pole". Science. 336 (6082): 694–697. Bibcode:2012Sci...336..694S. doi:10.1126/science.1223272. PMID 22582256.
  24. ^ Jutzi, M.; et al. (2013). "The structure of the asteroid 4 Vesta as revealed by models of planet-scale collisions". Nature. 494 (7436): 207–210. Bibcode:2013Natur.494..207J. doi:10.1038/nature11892. PMID 23407535.
  25. ^ Carruba, V.; et al. (2005). "On the V-type asteroids outside the Vesta family. I. Interplay of nonlinear secular resonances and the Yarkovsky effect: the cases of 956 Elisa and 809 Lundia". Astronomy and Astrophysics. 441 (2): 819–829. arXiv:astro-ph/0506656. Bibcode:2005A&A...441..819C. doi:10.1051/0004-6361:20053355.
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  27. ^ Roig, F.; et al. (2008). "V-type asteroids in the middle main belt". Icarus. 194 (1): 125–136. arXiv:0707.1012. Bibcode:2008Icar..194..125R. doi:10.1016/j.icarus.2007.10.004.
  28. ^ Michtchenko, T.A.; et al. (2002). "Origin of the basaltic asteroid 1459 Magnya: A dynamical and mineralogical study of the outer main belt". Icarus. 158 (2): 343–359. Bibcode:2002Icar..158..343M. doi:10.1006/icar.2002.6871.
  29. ^ Carvano, J.M.; et al. (2010). "SDSS-based taxonomic classification and orbital distribution of main belt asteroids". Astronomy and Astrophysics. 510: A43. Bibcode:2010A&A...510A..43C. doi:10.1051/0004-6361/200913322.
  30. ^ DeMeo, F.E.; et al. (2009). "An extension of the Bus asteroid taxonomy into the near-infrared". Icarus. 202 (1): 160–180. Bibcode:2009Icar..202..160D. doi:10.1016/j.icarus.2009.02.005.
  31. ^ Bus, S.J.; Binzel, R.P. (2002). "Phase II of the Small Main-Belt Asteroid Spectroscopic Survey: The Observations". Icarus. 158 (1): 106–145. Bibcode:2002Icar..158..106B. doi:10.1006/icar.2002.6857.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  32. ^ Russell, C.T.; Raymond, C.A. (2011). "The Dawn Mission to Vesta and Ceres". Space Science Reviews. 163 (1–4): 3–23. Bibcode:2011SSRv..163....3R. doi:10.1007/s11214-011-9836-2.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  33. ^ Hardersen, P.S.; et al. (2018). "Basaltic asteroid (1459) Magnya: Possible fragment of Vesta or a distinct parent body?". AAS/Division for Planetary Sciences Meeting Abstracts. 50: 305.07. Bibcode:2018DPS....5030507H.
  34. ^ Burbine, T.H.; et al. (2009). "Olivine-pyroxene distribution of S-type asteroids throughout the main belt". Meteoritics & Planetary Science. 44 (9): 1331–1341. Bibcode:2009M&PS...44.1331B. doi:10.1111/j.1945-5100.2009.tb01225.x.
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  36. ^ McSween, H.Y.; et al. (2013). "Dawn; the Vesta-HED connection; and the geologic context for eucrites, diogenites, and howardites". Meteoritics & Planetary Science. 48 (11): 2090–2104. Bibcode:2013M&PS...48.2090M. doi:10.1111/maps.12108.
  37. ^ Binzel, R.P.; et al. (2019). "Compositional distributions and evolutionary processes for the near-Earth object population: Results from the MIT-Hawaii Near-Earth Object Spectroscopic Survey (MITHNEOS)". Icarus. 324: 41–76. arXiv:2004.05090. Bibcode:2019Icar..324...41B. doi:10.1016/j.icarus.2018.12.035.
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