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25143 Itokawa (/ˌtˈkɑːwə/; Japanese: イトカワ,いとかわ,糸川 [itokaɰa]) is a stony sub-kilometer asteroid, classified as near-Earth object of the Apollo group and potentially hazardous asteroid, that measures approximately 350 meters in diameter. It was the first asteroid to be the target of a sample return mission, the Japanese space probe Hayabusa, and the smallest asteroid photographed and visited by a spacecraft.

25143 Itokawa
Hayabausa Image of the asteroid Itokawa.jpg
Grayscale image of 25143 Itokawa obtained by JAXA's Hayabusa spacecraft
Discovery [1]
Discovered byLINEAR
Discovery siteLincoln Lab's ETS
Discovery date26 September 1998
MPC designation(25143) Itokawa
Named after
Hideo Itokawa
(Japanese rocket scientist)[2]
1998 SF36
Apollo · NEO · PHA[1][3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Aphelion1.6951 AU
Perihelion0.9531 AU
1.3241 AU
1.52 yr (557 days)
Earth MOID0.0129 AU · 5 LD
Physical characteristics
Dimensions535 × 294 × 209 m[4]
mean diameter in meters:
313 m[5]
330 m[1]
350 m[6][7]
Mass(3.51±0.105)×1010 kg[4] (3.58±0.18)×1010 kg[8]
Mean density
1.9 ±0.13 g/cm³[4]
1.95±0.14 g/cm³[8]
12 h[9]
12.1 h[10]
12.12 h[11]
12.13 h[12]
12.132 h[6][13]
12.1323±0.0002 h[14]
12.1324 h[15]
12.15 h[16]
12.09±0.01 h[17]
SMASS = S (IV)[1] · Sqw [20] · S[21] · Q[6]
18.61[12] · 18.95 (R)[15] · 19.00[21] · 19.2[1] · 19.48[6][7] · 19.51±0.09[5] · 19.73[22]


Discovery and namingEdit

The asteroid was discovered in 1998 by the LINEAR project at the Lincoln Laboratory's Experimental Test Site in Socorro, New Mexico. It was given the provisional designation 1998 SF36. This minor planet was named after Hideo Itokawa (1912–1999), a Japanese rocket scientist.[23] The official naming citation was published in the Minor Planet Center on 6 August 2003 (M.P.C. 49281).[24]


Itokawa is an S-type asteroid. Radar imaging by Goldstone in 2001 observed an ellipsoid 630 ± 60 m long and 250 ± 30 m wide.[25][26]

The Hayabusa mission confirmed these findings and also suggested that Itokawa may be a contact binary formed by two or more smaller asteroids that have gravitated toward each other and stuck together. The Hayabusa images show a surprising lack of impact craters and a very rough surface studded with boulders, described by the mission team as a 'rubble pile'.[27] Furthermore, the density of the asteroid is too low for it to be made from solid rock. This would mean that Itokawa is not a monolith but rather a 'rubble pile' formed from fragments that have cohered over time. Based on Yarkovsky–O'Keefe–Radzievskii–Paddack effect measurements, a small section of Itokawa is estimated to have a density of 2.9 g/cm³, whereas a larger section is estimated to have a density of 1.8 g/cm³.[28]

Animation of 25143 Itokawa orbit
Lime: Itokawa ; Blue: Earth; Yellow: Sun;
Itokawa's orbit
This artist’s impression, based on detailed spacecraft observations, shows the strange peanut-shaped asteroid Itokawa.


In 2000, it was selected as the target of Japan's Hayabusa mission. The probe arrived in the vicinity of Itokawa on 12 September 2005 and initially "parked" in an asteroid–Sun line at 20 km (12 mi), and later 7 km (4.3 mi), from the asteroid (Itokawa's gravity was too weak to provide an orbit, so the spacecraft adjusted its orbit around the Sun until it matched the asteroid's). Hayabusa landed on 20 November for thirty minutes, but it failed to operate a device designed to collect soil samples. On 25 November, a second landing and sampling sequence was attempted. The sample capsule was returned to Earth and landed at Woomera, South Australia on 13 June 2010, around 13:51 UTC (23:21 local). On 16 November 2010, the Japan Aerospace Exploration Agency reported that dust collected during Hayabusa's voyage was indeed from the asteroid.[29]

Surface featuresEdit

Names of major surface features were proposed by Hayabusa scientists and accepted by the Working Group for Planetary System Nomenclature of the International Astronomical Union. Also, the Hayabusa science team is using working names for smaller surface features.[30][31] The following tables list the names of geological features on the asteroid.[32] No naming conventions have been disclosed for surface features on Itokawa.


Crater Coordinates Diameter
Eponym Ref
Catalina 17°S 14°E / 17°S 14°E / -17; 14 (Catalina) 0.02 2009 Catalina Station (astronomical observatory) in Arizona, United States WGPSN
Fuchinobe 34°N 91°W / 34°N 91°W / 34; -91 (Fuchinobe) 0.04 2009 Fuchinobe in Sagamihara, Japan WGPSN
Gando 76°S 155°W / 76°S 155°W / -76; -155 (Gando) n.a. 2009 Gando, Canary Islands; Spanish launch facility WGPSN
Hammaguira 18°S 155°W / 18°S 155°W / -18; -155 (Hammaguira) 0.03 2009 Hammaguir, Algeria; abandoned French launch site and missile testing range in the Sahara desert WGPSN
Kamisunagawa 28°S 45°E / 28°S 45°E / -28; 45 (Kamisunagawa) 0.01 2009 Kamisunagawa, town in Hokkaido Japan, where a microgravity test facility is located WGPSN
Kamoi 6°N 116°W / 6°N 116°W / 6; -116 (Kamoi) 0.01 2009 Japanese town of Kamoi in Yokohama, location of the NEC TOSHIBA Space Systems Ltd. factory WGPSN
Komaba 10°S 102°E / 10°S 102°E / -10; 102 (Komaba) 0.03 2009 Komaba in Meguro, Japan, where the Institute of Space and Astronautical Science is located WGPSN
Laurel 1°N 162°E / 1°N 162°E / 1; 162 (Laurel) 0.02 2009 U.S. city of Laurel in Maryland, where APL/JHU is located WGPSN
Miyabaru 40°S 116°W / 40°S 116°W / -40; -116 (Miyabaru) 0.09 2009 Radar site of the Uchinoura Space Center in Japan WGPSN
San Marco 28°S 41°W / 28°S 41°W / -28; -41 (San Marco) n.a. 2009 San Marco platform, an old oil platform near Kenya that served as a launch pad for Italian spacecraft WGPSN


Regiones (geologically distinct areas) on Itokawa.

Regio Named after
Arcoona Regio Arcoona, Australia
LINEAR Regio Lincoln Near-Earth Asteroid Research
MUSES-C Regio MUSES-C, name of the Hayabusa probe prior to launch.
Ohsumi Regio Ōsumi Peninsula
Sagamihara Regio Sagamihara, a town in Japan where Institute of Space and Astronautical Science is located.
Uchinoura Regio Uchinoura, a town in Japan (now part of Kimotsuki), the location of Uchinoura Space Center, Hayabusa launch site.
Yoshinobu Regio Launch site in the Tanegashima Space Center, Japan.

Itokawa SamplesEdit

Analysis of particles reported in August 2011Edit

Schematic view of 25143 Itokawa[33]

The 26 August 2011 issue of Science devoted six articles to findings based on dust that Hayabusa had collected from Itokawa.[34] Scientists' analysis suggested that Itokawa was probably made up from interior fragments of a larger asteroid that broke apart.[35] Dust collected from the asteroid surface is thought to have been exposed there for about eight million years.[34]

Scientists used varied techniques of chemistry and mineralogy to analyze the dust from Itokawa.[35] Itokawa's composition was found to match the common type of meteorites known as "low-total-iron, low metal ordinary chondrites".[36] Another team of scientists determined that the dark iron color on the surface of Itokawa was the result of abrasion by micrometeoroids and high-speed particles from the Sun which had converted the normally whitish iron oxide coloring.[36]

2018 Hayabusa ResultsEdit

Two separate groups report water in different Itokawa particles.

Jin et al. report water in low-calcium pyroxene grains. The water's isotope level corresponds with inner solar system and carbonaceous chondrite water isotope levels.[37]

Daly et al. report "OH and H2O" apparently formed by implantation of solar wind hydrogen. The rims of an olivine particle "show an enrichment of up to ~1.2 at % in OH and H20".[38]

The water concentrations of the Itokawa grains would indicate an estimated BSI (Bulk Silicate Itokawa) water content in line with Earth's bulk water, and that Itokawa had been a "water-rich asteroid".[39]

See alsoEdit


  1. ^ a b c d e f "JPL Small-Body Database Browser: 25143 Itokawa (1998 SF36)" (2016-01-24 last obs.). Jet Propulsion Laboratory. Retrieved 15 August 2017.
  2. ^ Schmadel, Lutz D. (2006). "(25143) Itokawa [1.32, 0.28, 1.6]". Dictionary of Minor Planet Names – (25143) Itokawa, Addendum to Fifth Edition: 2003–2005. Springer Berlin Heidelberg. p. 188. doi:10.1007/978-3-540-34361-5_2203. ISBN 978-3-540-34361-5.
  3. ^ "25143 Itokawa (1998 SF36)". Minor Planet Center. Retrieved 15 August 2017.
  4. ^ a b c Akira Fujiwara, et al., The Rubble-Pile Asteroid Itokawa as Observed by Hayabusa, Science, Vol. 312. no. 5778, pp. 1330 – 1334, 2 June 2006
  5. ^ a b c Mueller, Michael; Delbo', M.; Hora, J. L.; Trilling, D. E.; Bhattacharya, B.; Bottke, W. F.; et al. (April 2011). "ExploreNEOs. III. Physical Characterization of 65 Potential Spacecraft Target Asteroids". The Astronomical Journal. 141 (4): 9. Bibcode:2011AJ....141..109M. doi:10.1088/0004-6256/141/4/109.
  6. ^ a b c d "LCDB Data for (25143) Itokawa". Asteroid Lightcurve Database (LCDB). Retrieved 15 August 2017.
  7. ^ a b c Sekiguchi, T.; Abe, M.; Boehnhardt, H.; Dermawan, B.; Hainaut, O. R.; Hasegawa, S. (January 2003). "Thermal observations of MUSES-C mission target (25143) 1998 SF36". Astronomy and Astrophysics. 397: 325–328. Bibcode:2003A&A...397..325S. doi:10.1051/0004-6361:20021437. Retrieved 15 August 2017.
  8. ^ a b Shinsuke Abe, et al., Mass and Local Topography Measurements of Itokawa by Hayabusa, Science, Vol. 312. no. 5778, pp. 1344 – 1347, 2 June 2006
  9. ^ Lambert, J. S.; Tholen, D. J. (December 2001). "Rotational Studies of MUSES-C Target Asteroid (25143) 1998 SF36". American Astronomical Society. 33: 1402. Bibcode:2001AAS...199.6303L. Retrieved 15 August 2017.
  10. ^ Lowry, S. C.; Weissman, P. R.; Hicks, M. D. (November 2001). "CCD Observations of Asteroid 1998 SF36 (25143)". American Astronomical Society. 33: 1150. Bibcode:2001DPS....33.5909L. Retrieved 15 August 2017.
  11. ^ Lowry, Stephen C.; Weissman, Paul R.; Hicks, Michael D.; Whiteley, Robert J.; Larson, Steve (August 2005). "Physical properties of Asteroid (25143) Itokawa—Target of the Hayabusa sample return mission". Icarus. 176 (2): 408–417. Bibcode:2005Icar..176..408L. doi:10.1016/j.icarus.2005.02.002. Retrieved 15 August 2017.
  12. ^ a b Dermawan, Budi; Nakamura, Tsuko; Fukushima, Hideo; Sato, Hideo; Yoshida, Fumi; Sato, Yusuke (August 2002). "CCD Photometry of the MUSES-C Mission Target: Asteroid (25143) 1998 SF36". Publications of the Astronomical Society of Japan. 54 (4): 635–640. Bibcode:2002PASJ...54..635D. doi:10.1093/pasj/54.4.635. Retrieved 15 August 2017.
  13. ^ Kaasalainen, M.; Kwiatkowski, T.; Abe, M.; Piironen, J.; Nakamura, T.; Ohba, Y.; et al. (July 2003). "CCD photometry and model of MUSES-C target (25143) 1998 SF36". Astronomy and Astrophysics. 405 (3): L29–L32. Bibcode:2003A&A...405L..29K. doi:10.1051/0004-6361:20030819. Retrieved 15 August 2017.
  14. ^ Durech, J.; Vokrouhlický, D.; Kaasalainen, M.; Weissman, P.; Lowry, S. C.; Beshore, E.; et al. (September 2008). "New photometric observations of asteroids (1862) Apollo and (25143) Itokawa – an analysis of YORP effect". Astronomy and Astrophysics. 488 (1): 345–350. Bibcode:2008A&A...488..345D. doi:10.1051/0004-6361:200809663. Retrieved 15 August 2017.
  15. ^ a b Nishihara, S.; Abe, M.; Hasegawa, S.; Ishiguro, M.; Kitazato, K.; Miura, N.; et al. (March 2005). "Ground-based Lightcurve Observation of (25143) Itokawa, 2001–2004". 36th Annual Lunar and Planetary Science Conference. 36: 1833. Bibcode:2005LPI....36.1833N. Retrieved 15 August 2017.
  16. ^ Ohba, Y.; Abe, M.; Hasegawa, S.; Ishiguro, M.; Kwiatkowski, T.; Colas, F.; et al. (June 2003). "Pole orientation and triaxial ellipsoid shape of (25143) 1998 SF36, a target asteroid of the MUSES-C* mission". Earth. 55: 341–347.(EP&SHomepage). Bibcode:2003EP&S...55..341O. Retrieved 15 August 2017.
  17. ^ Warner, Brian D. (September 2004). "Lightcurve analysis for numbered asteroids 301, 380, 2867, 8373, 25143, and 31368". The Minor Planet Bulletin. 31 (3): 67–70. Bibcode:2004MPBu...31...67W. ISSN 1052-8091. Retrieved 15 August 2017.
  18. ^ Thomas, C. A.; Trilling, D. E.; Emery, J. P.; Mueller, M.; Hora, J. L.; Benner, L. A. M.; et al. (September 2011). "ExploreNEOs. V. Average Albedo by Taxonomic Complex in the Near-Earth Asteroid Population". The Astronomical Journal. 142 (3): 12. Bibcode:2011AJ....142...85T. doi:10.1088/0004-6256/142/3/85. Retrieved 15 August 2017.
  19. ^ S. M. Lederer, et al., Physical characteristics of Hayabusa target Asteroid 25143 Itokawa, Icarus, v. 173, p. 153–165 (2005)
  20. ^ Thomas, Cristina A.; Emery, Joshua P.; Trilling, David E.; Delbó, Marco; Hora, Joseph L.; Mueller, Michael (January 2014). "Physical characterization of Warm Spitzer-observed near-Earth objects". Icarus. 228: 217–246. arXiv:1310.2000. Bibcode:2014Icar..228..217T. doi:10.1016/j.icarus.2013.10.004. Retrieved 15 August 2017.
  21. ^ a b Carry, B.; Solano, E.; Eggl, S.; DeMeo, F. E. (April 2016). "Spectral properties of near-Earth and Mars-crossing asteroids using Sloan photometry". Icarus. 268: 340–354. arXiv:1601.02087. Bibcode:2016Icar..268..340C. doi:10.1016/j.icarus.2015.12.047. Retrieved 15 August 2017.
  22. ^ Abe, M.; Ohba, Y.; Ishiguro, M.; Hasegawa, S.; Fuse, T.; Aoki, K.; et al. (March 2002). "Physical Model and Taxonomic Type of 1998 SF36, the Target Asteroid of Sample Return Mission, MUSES-C". 33rd Annual Lunar and Planetary Science Conference. 33: 1666. Bibcode:2002LPI....33.1666A. Retrieved 15 August 2017.
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  24. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 15 August 2017.
  25. ^ Ostro, S. J.; Benner, L. A. M.; Nolan, M. C.; Giorgini, J. D.; Jurgens, R. F.; Rose, R.; Yeomans, D. K. (2001). "Radar Observations of Asteroid 25143 (1998 SF36)". Bulletin of the American Astronomical Society. 33: 1117. Bibcode:2001DPS....33.4113O.
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  27. ^ "Hayabusa: Itokawa Beckons as Japan's Spacecraft Searches for Places to Touch Down". Archived from the original on 12 May 2008. Retrieved 11 August 2008.CS1 maint: BOT: original-url status unknown (link)
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  29. ^ Atkinson, Nancy (16 November 2010). "Confirmed: Hayabusa Nabbed Asteroid Particles". Universe Today. Archived from the original on 6 December 2010. Retrieved 16 November 2010.
  30. ^ "Itowaka Geological Map". Archived from the original on 26 February 2009. Retrieved 11 August 2008.CS1 maint: BOT: original-url status unknown (link)
  31. ^ "Local site names on Itowaka". Archived from the original on 26 February 2009. Retrieved 11 August 2008.CS1 maint: BOT: original-url status unknown (link)
  32. ^ USGS: Itokawa nomenclature
  33. ^ "The Anatomy of an Asteroid". ESO Press Release. Retrieved 6 February 2014.
  34. ^ a b "Asteroid Dust Confirms Meteorite Origins". New York Times. 25 August 2011. Retrieved 26 August 2011.
  35. ^ a b Nakamura, Tomoki; Noguchi, Takaaki; Tanaka, Masahiko; Zolensky, Michael E.; Kimura, Makoto; Tsuchiyama, Akira; Nakato, Aiko; Ogami, Toshihiro; Ishida, Hatsumi; Uesugi, Masayuki; Yada, Toru; Shirai, Kei; Fujimura, Akio; Okazaki, Ryuji; Sandford, Scott A.; Ishibashi, Yukihiro; Abe, Masanao; Okada, Tatsuaki; Ueno, Munetaka; Mukai, Toshifumi; Yoshikawa, Makoto; Kawaguchi, Junichiro (26 August 2011). "Itokawa Dust Particles: A Direct Link Between S-Type Asteroids and Ordinary Chondrites". Science. 333 (6046): 1113–6. Bibcode:2011Sci...333.1113N. doi:10.1126/science.1207758. PMID 21868667. Retrieved 26 August 2011.
  36. ^ a b "Most Earth meteorites linked to single asteroid". Los Angeles Times. 26 August 2011. Retrieved 26 August 2011.
  37. ^ Jin ZL, Bose M, Peeters Z (2018). "New Clues to Ancient Water on Itokawa". Lunar and Planetary Science Conference (2083): 1670. Bibcode:2018LPI....49.1670J.
  38. ^ Daly, L; Lee, M; Hallis, L; Bland, P; Reddy, S; et al. (2018). "The origin of hydrogen in space weathered rims of Itokawa regolith particles". 2018 Hayabusa Symposium.
  39. ^ Jin Z; Bose M (2018). "Establishing Itokawa's water contribution to Earth". 2018 Hayabusa Symposium.

Further readingEdit

External linksEdit