25143 Itokawa

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25143 Itokawa

Discovery A
Discoverer	LINEAR
Discovery date	September 26, 1998
Alternate designations B	1998 SF36
Category	Apollo asteroid, Mars-crosser asteroid
Orbital elements C
Epoch August 18, 2005 (JD 2453600.5)
Eccentricity (e)	0.280
Semi-major axis (a)	198.044 Gm (1.324 AU)
Perihelion (q)	142.568 Gm (0.953 AU)
Aphelion (Q)	253.520 Gm (1.695 AU)
Orbital period (P)	556.355 d (1.52 a)
Mean orbital speed	25.37 km/s
Inclination (i)	1.622°
Longitude of the ascending node (Ω)	69.095°
Argument of perihelion (ω)	162.760°
Mean anomaly (M)	294.502°
Physical characteristics D
Dimensions	535 × 294 × 209 m [1]
Mass	(3.51±0.105)×1010 kg [1], (3.58±0.18)×1010 kg [2]
Density	1.9 ±0.13 g/cm³ [1], 1.95 ± 0.14 g/cm³ [2]
Surface gravity	~0.0001 m/s²
Escape velocity	~0.0002 km/s
Rotation period	0.5055 d (12.132 h) [3]
Spectral class	S
Absolute magnitude	19.2
Albedo (geometric)	0.53
Mean surface temperature	~206 K
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25143 Itokawa (IPA [itokawa], Japanese イトカワ or 糸川) is an Apollo and Mars-crosser asteroid. It is was the focus of detailed study by the Japanese space probe Hayabusa and may become the first asteroid sample-return target.

Contents 1 History 2 Description 3 Hayabusa mission 4 Named surface features 5 References 6 External links

[edit] History

The asteroid was discovered in 1998 by the LINEAR project, and given the provisional designation 1998 SF₃₆. In 2000, it was selected as the target of Japan's Hayabusa mission. Soon thereafter, it was officially named after Hideo Itokawa, a Japanese rocket scientist.

[edit] Description

Itokawa is an S-type asteroid. Radar imaging by Goldstone revealed an elongated irregular shape. [1]

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, these particular boulders were referred by the mission team, as being in a 'rubble'. [2] This would mean that Itokawa is not a monolith but rather a ‘rubble pile’ formed from fragments that have cohered over time.

[edit] Hayabusa mission

The Japanese probe Hayabusa arrived in the vicinity of Itokawa on September 12, 2005 and initially "parked" in an asteroid-sun line at 20 km, and later 7 km, from the asteroid. Hayabusa landed November 20 for thirty minutes, but failed to operate a device designed to collect soil samples. On November 25, a second landing and the sampling sequence was attempted. Hayabusa has since left the asteroid, and the sample capsule is planned to land at Woomera, South Australia in 2010; although, it is unclear if any samples were collected.

[edit] Named surface features

Names of major features were proposed by Hayabusa scientists and accepted by the Working Group for Planetary System Nomenclature of the International Astronomical Union. See the list of geological features on 25143 Itokawa.

Also, the Hayabusa science team is using working names for smaller surface features. [3] [4]

[edit] References

1. ^ ^{a b c} Akira Fujiwara, et al., The Rubble-Pile Asteroid Itokawa as Observed by Hayabusa, Science, Vol. 312. no. 5778, pp. 1330 - 1334, June 2, 2006
2. ^ ^{a b} Shunsuke Abe, et al., Mass and Local Topography Measurements of Itokawa by Hayabusa, Science, Vol. 312. no. 5778, pp. 1344 - 1347, June 2, 2006
3. ^ M. Kaasalainen, et al., CCD photometry and model of MUSES-C target (25143) 1998 SF36, Astronomy and Astrophysics, v.405, p.L29-L32 (2003)

[edit] External links

• Gazetteer of Planetary Nomenclature
• MIT's LINEAR asteroid named for Japan's 'Dr. Rocket' (MIT press release)
• Latest news and images from Hayabusa (JAXA Hayabusa official page)
• Hayabusa's Scientific and Engineering Achievements during Proximity Operations around Itokawa (JAXA press release)
• Earth impact probability of the Asteroid (25143) Itokawa to be sampled by the spacecraft Hayabusa (paper abstract)
• Astronomy Picture Of The Day: Approaching Asteroid Itokawa, A Robot's Shadow on Asteroid Itokawa, The Missing Craters of Asteroid Itokawa, Smooth Sections on Asteroid Itokawa
• Special issue: Hayabusa at Itokawa, Science, Vol. 312, no. 5778, June 2 2006
• Initial Scientific Results of Hayabusa’s Investigation on Itokawa ~Summary of the Special Issue of “Science”Magazine~ (ISAS/JAXA press release)

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