25143 Itokawa

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**25143 Itokawa**
Discovery
Discovered by:	LINEAR
Discovery date:	September 26, 1998
Alternative names:	1998 SF₃₆
Minor planet category:	Apollo asteroid, Mars-crosser asteroid
Orbital characteristics
Epoch August 18, 2005 (JD 2453600.5)
Aphelion distance:	253.520 Gm (1.695 AU)
Perihelion distance:	142.568 Gm (0.953 AU)
Semi-major axis:	198.044 G m (1.324 AU)
Eccentricity:	0.280
Orbital period:	556.355 d (1.52 a)
Avg. orbital speed:	25.37 km/s
Mean anomaly:	294.502°
Inclination:	1.622°
Longitude of ascending node:	69.095°
Argument of perihelion:	162.760°
Physical characteristics
Dimensions:	535 × 294 × 209 m ^[1]
Mass:	(3.51±0.105)×10¹⁰ kg ^[1], (3.58±0.18)×10¹⁰ kg ^[2]
Mean density:	1.9 ±0.13 g/cm³ ^[1], 1.95 ± 0.14 g/cm³ ^[2]
Equatorial surface gravity:	~0.0001 m/s²
Escape velocity:	~0.0002 km/s
Rotation period:	0.5055 d (12.132 h) ^[3]
Albedo:	0.53
Temperature:	~206 K
Spectral type:	S
Absolute magnitude:	19.2

25143 Itokawa (IPA [itokawa], Japanese イトカワ or 糸川) is an Apollo and Mars-crosser asteroid. It was the focus of detailed study by the Japanese space probe Hayabusa and may become the first asteroid sample-return target.

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; however, it is unclear if any samples were collected.